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1

RAPID AND ACCURATE METHOD FOR ESTIMATING MOLECULAR WEIGHTS OF ORGANIC COMPOUNDS FROM LOW RESOLUTION MASS SPECTRA  

EPA Science Inventory

An improved method of estimating molecular weights of volatile organic compounds from their mass spectra has been developed and evaluated for accuracy. his technique can be implemented with a user friendly expert system on a personal computer. he method is based on a pattern reco...

2

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).

2013-06-17

3

Molecular Weight of Native Cellulose  

Microsoft Academic Search

THE molecular weight of cellulose is of great interest to cellulose chemistry, and many attempts have been made to determine it. The cellulose derivatives, esters and ethers, can in general be dissolved in simple organic solvents, and their molecular weights determined by the osmotic pressure method. It is questionable, however, if the derivatives can be prepared without degradation of the

Nils Gralén

1943-01-01

4

How accurately do we estimate patients' weight in emergency departments?  

PubMed Central

OBJECTIVE: To assess the accuracy of estimates of patients' weight made by physicians, nurses, and patients themselves in emergency departments. DESIGN: Observational prospective study. SETTING: Tertiary referral centre in Vancouver, BC. PARTICIPANTS: Eleven attending physicians, 26 nurses, and a convenience sample of 117 patients. INTERVENTIONS: Patients themselves, attending physicians, and nurses independently estimated the weight of 117 patients. An investigator weighed each patient. MAIN OUTCOME MEASURES: Mean error was determined by subtracting actual weight from estimated weight and dividing by actual weight; 95% confidence intervals (CI) were calculated. RESULTS: Mean error in estimates was 3.1% (95% CI 2.7 to 3.5) for patients, 8.4% for nurses (CI 7.6 to 9.2), and 8.1% (CI 7.1 to 9.1) for physicians. Weight was estimated within 5% of actual weight by 32% of nurses, 39% of physicians, and 82% of patients. Weight was estimated within 10% of actual weight by 66% of nurses, 66% of physicians, and 97% of patients. Estimates out by more than 15% were made by 11% of nurses, 16% of physicians, and 1% of patients. CONCLUSIONS: Patient estimates were most accurate. Physician and nurse estimates were unreliable.

Fernandes, C. M.; Clark, S.; Price, A.; Innes, G.

1999-01-01

5

An accurate integral equation for molecular fluids.  

NASA Astrophysics Data System (ADS)

Tests of several closures for the Ornstein-Zernike equation in the case of hard spheres are considered. The best of these is extended to the case of molecular fluids and solved for a hard homonuclear diatomic fluid. The theory used is a modification of an earlier theory originally proposed by Verlet for the hard sphere system, which we denote as the VM theory. The results are compared with computer simulation data and with the results of the Percus-Yevick (PY) and Nonspherical Bridge Function (NSB) theories. The VM theory produces excellent results for the compressibility factor and the spherical harmonic coefficients of the pair distribution function up to a packing fraction of 0·47 and a reduced elongation of 1·0. The NSB results are not as accurate, and the PY results are less accurate still. The bridge function given by the VM, NSB, and PY closures are compared with that extracted from computer simulation pair distribution function data. The VM theory gives good agreement and is similarly superior to the NSB and PY theories.

Labík, S.; Malijevský, A.; Smith, W. R.

6

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

7

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...

2009-01-01

8

Molecular weights of lignite macromolecules  

SciTech Connect

A sample of the base-extractable product from the 4-nitroperbenzoic acid oxidation of lignite was converted to the methylated derivative with dimethyl sulfate followed by diazomethane in DMF-ether, and was reductively acetylated with zinc dust in acetic anhydride as in the humic acid derivatization above. A light tan THF-soluble material was obtained. The molecular weight was determined in the static LALLS cell in THF solution. A linear relationship was obtained in the Kc/R/sub theta/ versus c plot (r/sup 2/ = 0.95). The molecular weight obtained for the derivative of the oxidation product (1.3 x 10/sup 6/) was the same as the value obtained for the humic acid derivative. The reductively acetylated oxidation product was also examined with the SEC-LALLS-RI system. A symmetrical peak was observed for the LALLS response, and a nonsymmetrical peak for the RI response. Somewhat lower values for the number average, weight average and z average molecular weights were calculated from these data (Mn = 6.5 x 10/sup 5/, Mw = 7.8 x 10/sup 5/, Mz = 9.1 x 10/sup 5/). These data indicate that by oxidatively cleaving the benzyl ether groups with the peracid, a substantial macromolecule is produced which is comparable in size to that obtained by simple base extraction of the lignite. This implies that there is some basic unit of this molecular weight making up the coal structure, and that in base extraction some of these units are released, whereas in peracid oxidation a large number of them are released by scission of cross-linking bonds. 6 refs., 4 figs.

Olson, E.S.; Diehl, J.W.; Froehlich, M.L.

1985-10-01

9

Accurate Ab Initio Calculation of Molecular Constants.  

National Technical Information Service (NTIS)

Molecular constants have beenc omputed for the ground states (sup 2)Roman numeral 2 of (sup 17)OH and (sup 1)Sigma of (sup 107)AgH plus. The valence-bond method and advanced computational technique were used to perform all-electron ab initio calculation o...

S. Kotochigova I. Tupitsyn

1998-01-01

10

The Molecular Weight Distribution of Polymer Samples  

ERIC Educational Resources Information Center

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

Horta, Arturo; Pastoriza, M. Alejandra

2007-01-01

11

IRIS: Towards an Accurate and Fast Stage Weight Prediction Method  

NASA Astrophysics Data System (ADS)

The knowledge of the structural mass fraction (or the mass ratio) of a given stage, which affects the performance of a rocket, is essential for the analysis of new or upgraded launchers or stages, whose need is increased by the quick evolution of the space programs and by the necessity of their adaptation to the market needs. The availability of this highly scattered variable, ranging between 0.05 and 0.15, is of primary importance at the early steps of the preliminary design studies. At the start of the staging and performance studies, the lack of frozen weight data (to be obtained later on from propulsion, trajectory and sizing studies) leads to rely on rough estimates, generally derived from printed sources and adapted. When needed, a consolidation can be acquired trough a specific analysis activity involving several techniques and implying additional effort and time. The present empirical approach allows thus to get approximated values (i.e. not necessarily accurate or consistent), inducing some result inaccuracy as well as, consequently, difficulties of performance ranking for a multiple option analysis, and an increase of the processing duration. This forms a classical harsh fact of the preliminary design system studies, insufficiently discussed to date. It appears therefore highly desirable to have, for all the evaluation activities, a reliable, fast and easy-to-use weight or mass fraction prediction method. Additionally, the latter should allow for a pre selection of the alternative preliminary configurations, making possible a global system approach. For that purpose, an attempt at modeling has been undertaken, whose objective was the determination of a parametric formulation of the mass fraction, to be expressed from a limited number of parameters available at the early steps of the project. It is based on the innovative use of a statistical method applicable to a variable as a function of several independent parameters. A specific polynomial generator, validated on several technical and econometrical cases, has been used for this purpose. A database of several conventional stages, operated with either solid or liquid propellants, has been made up, in conjunction with an evolutionary set of geometrical, physical and functional parameters likely to contribute to the description of the mass fraction and presumably known at the early steps of the preliminary design. After several iterations aiming at selecting the most influential parameters, polynomial expressions of the mass fraction have been made up, associated to a confidence level. The outcome highlights the real possibility of a parametric formulation of the mass fraction for conventional stages on the basis of a limited number of descriptive parameters and with a high degree of accuracy, lower than 10%. The formulas have been later on tested on existing or preliminary stages not included in the initial database, for validation purposes. Their mass faction is assessed with a comparable accuracy. The polynomial generation method in use allows also for a search of the influence of each parameter. The devised method, suitable for the preliminary design phase, represents, compared to the classical empirical approach, a significant way of improvement of the mass fraction prediction. It enables a rapid dissemination of more accurate and consistent weight data estimates to support system studies. It makes also possible the upstream processing of the preliminary design tasks through a global system approach. This method, currently in the experimental phase, is already in use as a complementary means at the technical underdirectorate of CNES-DLA. * IRIS :Instrument de Recherche des Indices Structuraux

Taponier, V.; Balu, A.

2002-01-01

12

Effect of molecular weight on polymer processability  

Microsoft Academic Search

Differences in rheological behavior due to the polymer molecular weight and molecular weight distribution have been shown with the MPT. SBR polymers having high molecular weight fractions develop higher stress relaxation time values due to the higher degree of polymer entanglements. Tests conducted at increasing temperatures show the diminishing influence of the polymer entanglements upon stress relaxation time. EPDM polymers

Karg

1983-01-01

13

Effect of molecular weight on polymer processability  

SciTech Connect

Differences in rheological behavior due to the polymer molecular weight and molecular weight distribution have been shown with the MPT. SBR polymers having high molecular weight fractions develop higher stress relaxation time values due to the higher degree of polymer entanglements. Tests conducted at increasing temperatures show the diminishing influence of the polymer entanglements upon stress relaxation time. EPDM polymers show stress relaxation time and head pressure behavior which correlates with mill processability. As anticipated, compounded stock of EPDM have broad molecular weight distribution has higher stress relaxation time values than EPDM compounds with narrow molecular weight distribution.

Karg, R.F.

1983-01-01

14

Weight-An accurate, up-to-date, layman's definition  

NASA Astrophysics Data System (ADS)

The conventional definition of weight presented in physics textbooks is not what is popularly meant by weight, causes needless confusion in weightless situations, and is based upon a pre-1915 theory of gravitation. Arguments are presented in favor of a better definition.

Bishop, Roy

1999-04-01

15

Production of high molecular weight polylactic acid  

DOEpatents

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

Bonsignore, Patrick V. (Joilet, IL)

1995-01-01

16

Production of high molecular weight polylactic acid  

DOEpatents

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

Bonsignore, P.V.

1995-11-28

17

Hextend, High Molecular Weight Hydroxyethyl Starch 6% ...  

Center for Biologics Evaluation and Research (CBER)

... Hextend, High Molecular Weight Hydroxyethyl Starch 6% (Hetastarch) in Buffered Electrolyte Dextrose Solution. Product ... More results from www.fda.gov/biologicsbloodvaccines/bloodbloodproducts/approvedproducts

18

Ultrasonographic prediction of term birth weight: How accurate is it?  

Microsoft Academic Search

Objective: The purpose of this study was to investigate the accuracy of 25 ultrasonic algorithms for the estimation of term fetal weight and to compare these results to an equation that is based on maternal and pregnancy-specific characteristics alone. Study design: Ultrasonography was performed in 82 nondiabetic gravid women at 35 to 41 weeks of gestation. Fetal biparietal diameter, abdominal

Gerard G. Nahum; Harold Stanislaw

2003-01-01

19

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

Code of Federal Regulations, 2010 CFR

...ensure accurate weights. Such scales shall meet applicable requirements...contained in the General Code, Scale Code, and Weights Code...Superintendent of Documents, U.S. Government Printing Office, Washington...locations.html. (b) All scales used by stockyard...

2009-01-01

20

Molecular Weight Distribution of Wheat Proteins  

Microsoft Academic Search

Cereal Chem. 76(6):827-836 The molecular weight distribution (MWD) of wheat proteins is becoming recognized as the main determinant of physical dough prop- erties. Studies of high polymers have shown that properties such as tensile strength are related to a fraction of polymer with molecular weight above a critical value and the MWD of this fraction. Elongation to break is treated

M. Southan; F. MacRitchie

1999-01-01

21

Accurate measure by weight of liquids in industry. Final report  

SciTech Connect

This research`s focus was to build a prototype of a computerized liquid dispensing system. This liquid metering system is based on the concept of altering the representative volume to account for temperature changes in the liquid to be dispensed. This is actualized by using a measuring tank and a temperature compensating displacement plunger. By constantly monitoring the temperature of the liquid, the plunger can be used to increase or decrease the specified volume to more accurately dispense liquid with a specified mass. In order to put the device being developed into proper engineering perspective, an extensive literature review was undertaken on all areas of industrial metering of liquids with an emphasis on gravimetric methods.

Muller, M.R.

1992-12-12

22

Molecular weight determinations of biosolubilized coals.  

National Technical Information Service (NTIS)

We have compared several different methods for determining the molecular weight of biosolubilized coals: Aqueous gel permeation Chromatography (GPC), organic GPC, preparative GPC, dynamic laser light scattering (LLS), static LLS, static LLS, mass spectrom...

J. C. Linehan S. Clauss R. Bean J. Campbell

1991-01-01

23

Microdialysis unit for molecular weight separation  

SciTech Connect

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

Smith, R.D.; Liu, C.

1999-09-21

24

Hextend High Molecular Weight Hydroxyethyl Starch 6%  

Center for Biologics Evaluation and Research (CBER)

Text Version... Drug, and Cosmetic Act for Hextend, High Molecular Weight Hydroxyethyl Starch 6 ... to demonstrate that the drug product is safe and effective for use ... More results from www.fda.gov/downloads/biologicsbloodvaccines/bloodbloodproducts

25

Molecular Weight Determinations of Dimethylpolysiloxane Polymers.  

National Technical Information Service (NTIS)

Using a vapor phase osmometer and an automatic membrane osmometer the number-average molecular weight of two samples of dimethylpolysiloxane - 2300 and 8000 cstk - as well as samples made by mixing the two previously mentioned materials were determined. T...

Z. A. Luthey

1968-01-01

26

TOPICAL REVIEW: Highly accurate calculations of molecular electronic structure  

NASA Astrophysics Data System (ADS)

The highly accurate calculation of molecular electronic structure requires the expansion of the molecular electronic wavefunction to be as nearly complete as possible both in one- and n-electron space. In this review, we consider the convergence behaviour of computed electronic energies, in particular electronic enthalpies of reaction, as a function of the one-electron space. Based on the convergence behaviour, extrapolations to the limit of a complete one-electron basis are possible and such extrapolations are compared with the direct computation of electronic energies near the basis-set limit by means of explicitly correlated methods. The most elaborate and accurate computations are put into perspective with respect to standard and - from a computational point of view - inexpensive density functional, complete basis set (CBS) and Gaussian-2 calculations. Using the explicitly correlated coupled-cluster method including singles, doubles and non-iterative triples replacements, it is possible to compute (the electronic part of) enthalpies of reaction accurate to within 1 kJ mol-1. To achieve this level of accuracy with standard coupled-cluster methods, large basis sets or extrapolations to the basis-set limit are necessary to exploit fully the intrinsic accuracy of the coupled-cluster methods.

Klopper, Wim; Bak, Keld L.; Jørgensen, Poul; Olsen, Jeppe; Helgaker, Trygve

1999-07-01

27

The arbitrarily loaded single-edge cracked circular disc; accurate weight function solutions  

Microsoft Academic Search

Crack problems of a circular disc (cylinder) with an arbitrarily loaded radial edge crack have been analyzed using an accurate weight function method. An exact stress intensity factor for the uniform load case due to Gregory [3] was used as the reference solution for deriving the weight function. Particular attention was paid to assessing the accuracy of the new stress

X. R. Wu

1991-01-01

28

Molecular weights and molecular weight distributions of irradiated cellulose fibers by gel permeation chromatography. [. gamma. radiation  

Microsoft Academic Search

Radiation degradation of cellulose fibers was investigated by gel permeation chromatography (GPC). Scoured cotton of Mexican variety (cellulose I), Polynosic rayon (cellulose II), and their microcrystalline celluloses obtained by hydrolysis of the original fibers were irradiated by Co-60 ..gamma..-rays under vacuum or humid conditions. The irradiated samples were then nitrated under nondegradative conditions. The molecular weights and molecular weight distributions

Y. Kusama; E. Kageyama; M. Shimada; Y. Nakamura

1976-01-01

29

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

30

Formulary Management of Low Molecular Weight Heparins  

Microsoft Academic Search

Low molecular weight heparins (LMWHs) are increasingly being utilised as anticoagulants in healthcare settings. These agents offer several advantages over standard unfractionated heparin. Indications for LMWHs include deep vein thrombosis and pulmonary embolism prophylaxis, deep vein thrombosis treatment, use in coronary procedures associated with a high risk for bleeding, and in acute coronary syndromes. Prior to being added to formularies,

William E. Wade; Bradley C. Martin; Jeffrey A. Kotzan; William J. Spruill; Marie A. Chisoholm; Matthew Perri

2000-01-01

31

Low molecular weight fluids in EPDM  

Microsoft Academic Search

Ethylene propylene diene monomer (EPDM) is widely used in outdoor insulations. The electrical performance of the polymer material is influenced by the surface hydrophobicity which in turn is affected by the presence of low molecular weight (LMW) fluids on the surface and in the bulk. In the present paper, the LMW fluid is extracted using a solvent at an elevated

Liwen Cao; R. Hackam

1997-01-01

32

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

33

Accurate prediction of term birth weight from prospectively measurable maternal characteristics  

Microsoft Academic Search

Objective: To determine whether accurate prediction of term birth weight is possible based on maternal characteristics routinely measured remote from term, and to compare this technique to more expensive methods requiring obstetrical ultrasound examinations.Methods: Two hundred fifty-nine normal, non-smoking, non-diabetic Caucasian gravidas with uncomplicated term gestations were studied. Seven maternal characteristics (age, parity, height, weight, level of obesity, rate of

Gerard G. Nahum; Harold Stanislaw; B. Joyce Huffaker

1998-01-01

34

High Molecular Weight Fossil Porphyrins: Evidence for Monomeric and Dimeric Tetraphyrroles of About 1100 Molecular Weight.  

National Technical Information Service (NTIS)

Vanadyl porphyrin complexes of approximately 1100 molecular weight have been isolated from a Triassic and a Pennsylvanian oil shale by gel permeation chromatography. Adsorption chromatography resolved the pigments into two different structural types. The ...

M. Blumer M. Rudrum

1969-01-01

35

Effect of polymerization time on the molecular weight and molecular weight distribution of polypropylene  

Microsoft Academic Search

The influence of the polymerization time on the molecular weight (Mw, Mn, Mp, and Mz), molecular weight distribution (MWD) and relative MWD of polypropylene (PP) in the propylene polymerization with a Mg(OEt)2\\/DIBP\\/TiCl4\\/PTES\\/AlEt3 catalyst system in the slurry phase has been studied by using gel permeation chromatography (GPC), where Mg(OEt)2, DIBP (diisobutyl phthalate), TiCl4, PTES (phenyl triethoxy silane), and triethyl aluminum

S. Abedi; M. Hosseinzadeh; M. A. Kazemzadeh; Majid Daftari-Besheli

2006-01-01

36

Antigenicity of low molecular weight surfactant species.  

PubMed Central

The authors tested the antigenicity of human lung surfactant isolated from amniotic fluid. Mice and rabbits were immunized. Rabbit polyclonal antisera to these surfactant preparations were absorbed with normal human plasma proteins. Polyclonal antisera reacted with both high molecular weight (35 kd) surfactant apoprotein and to lower molecular weight species, both 18 kd and 9 kd. Mice were used to generate monoclonal antibodies to surfactant. Enzyme-linked immunosorbant assay was used to identify five monoclonal antibodies that reacted with surfactant. By Western blot analysis, all of these recognized a low molecular weight surfactant species (9 kd) that could be either SP-B or SP-C. One reacted with a 37 kd protein in the surfactant preparation, consistent with SP-A. One monoclonal antibody also recognized a higher molecular weight species (44 kd) of unknown origin. The ability of antisera and monoclonal antibodies to inhibit the functional activity of surfactant was assayed using a pulsating bubble surfactometer. Rabbit polyclonal antisera inhibited initial surface adsorption to equilibrium surface tension and increased the minimum surface tension after 1 and 5 minutes of initiation of pulsations. This inhibitory activity of the antisera was noted in divalent F(ab')2 fragments. Monovalent F(ab) fragments and control normal rabbit sera did not inhibit surfactant function in this assay. Of the anti-surfactant monoclonal antibodies that reacted with surfactant by ELISA and Western blot, three inhibited its capacity to lower surface tension on the pulsating bubble apparatus. The other two monoclonal antibodies showed no functional inhibitory activity. It is concluded that both the 35 kd SP-A and the 9 kd proteins of human surfactant are highly immunogenic and partially crossreactive. Resulting antibodies could alter the ability of surfactant to perform its physiologic function, ie, to lower surface tension. Images Figure 1A, B

Strayer, D. S.; Merritt, T. A.; Makunike, C.; Hallman, M.

1989-01-01

37

Molecular Weight of alpha-Amylase  

Microsoft Academic Search

PROF. KURT H. MEYER and his co-workers1,2 have recently succeeded in the crystallization of alpha-amylase from pig's pancreas. The molecular weight of the substance, kindly supplied by Prof. Meyer, has been determined from sedimentation and diffusion experiments. The dried substance was dissolved in a buffer solution of pH 8.4, with a molarity of 0.2 in sodium chloride, 0.02 in boric

Carl-Erik Danielsson

1947-01-01

38

Molecular Weight of Malt-Amylase  

Microsoft Academic Search

IN an earlier investigation1, the molecular weight of alpha-amylase from pig's pancreas2,3 Was found to be 45,000, as calculated from the values4 s20 = 4.50 S, D = 8.05 × 10-7 C.G.S. and V20 = 0.70. At this Institute a new method for the isolation of amylase from malt has been developed5. It was shown that by repeated purification of

Carl-Erik Danielsson

1948-01-01

39

A live weight-heart girth relationship for accurate dosing of east African shorthorn zebu cattle.  

PubMed

The accurate estimation of livestock weights is important for many aspects of livestock management including nutrition, production and appropriate dosing of pharmaceuticals. Subtherapeutic dosing has been shown to accelerate pathogen resistance which can have subsequent widespread impacts. There are a number of published models for the prediction of live weight from morphometric measurements of cattle, but many of these models use measurements difficult to gather and include complicated age, size and gender stratification. In this paper, we use data from the Infectious Diseases of East Africa calf cohort study and additional data collected at local markets in western Kenya to develop a simple model based on heart girth circumference to predict live weight of east African shorthorn zebu (SHZ) cattle. SHZ cattle are widespread throughout eastern and southern Africa and are economically important multipurpose animals. We demonstrate model accuracy by splitting the data into training and validation subsets and comparing fitted and predicted values. The final model is weight(0.262) = 0.95 + 0.022 × girth which has an R (2) value of 0.98 and 95 % prediction intervals that fall within the ± 20 % body weight error band regarded as acceptable when dosing livestock. This model provides a highly reliable and accurate method for predicting weights of SHZ cattle using a single heart girth measurement which can be easily obtained with a tape measure in the field setting. PMID:22923040

Lesosky, Maia; Dumas, Sarah; Conradie, Ilana; Handel, Ian Graham; Jennings, Amy; Thumbi, Samuel; Toye, Phillip; Bronsvoort, Barend Mark de Clare

2012-08-25

40

W-AlignACE: an improved Gibbs sampling algorithm based on more accurate position weight matrices learned from sequence and gene expression\\/ChIP-chip data  

Microsoft Academic Search

Motivation: Position weight matrices (PWMs) are widely used to depict the DNA binding preferences of transcription factors (TFs) in computational molecular biology and regulatory genomics. Thus, learning an accurate PWM to characterize the binding sites of a specific TF is a fundamental problem that plays an important role in modeling regulatory motifs and also in discovering the regulatory targets of

Xin Chen; Lingqiong Guo; Zhaocheng Fan; Tao Jiang

2008-01-01

41

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

ERIC Educational Resources Information Center

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

Izunobi, Josephat U.; Higginbotham, Clement L.

2011-01-01

42

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

43

Accurate response surface approximations for weight equations based on structural optimization  

NASA Astrophysics Data System (ADS)

Accurate weight prediction methods are vitally important for aircraft design optimization. Therefore, designers seek weight prediction techniques with low computational cost and high accuracy, and usually require a compromise between the two. The compromise can be achieved by combining stress analysis and response surface (RS) methodology. While stress analysis provides accurate weight information, RS techniques help to transmit effectively this information to the optimization procedure. The focus of this dissertation is structural weight equations in the form of RS approximations and their accuracy when fitted to results of structural optimizations that are based on finite element analyses. Use of RS methodology filters out the numerical noise in structural optimization results and provides a smooth weight function that can easily be used in gradient-based configuration optimization. In engineering applications RS approximations of low order polynomials are widely used, but the weight may not be modeled well by low-order polynomials, leading to bias errors. In addition, some structural optimization results may have high-amplitude errors (outliers) that may severely affect the accuracy of the weight equation. Statistical techniques associated with RS methodology are sought in order to deal with these two difficulties: (1) high-amplitude numerical noise (outliers) and (2) approximation model inadequacy. The investigation starts with reducing approximation error by identifying and repairing outliers. A potential reason for outliers in optimization results is premature convergence, and outliers of such nature may be corrected by employing different convergence settings. It is demonstrated that outlier repair can lead to accuracy improvements over the more standard approach of removing outliers. The adequacy of approximation is then studied by a modified lack-of-fit approach, and RS errors due to the approximation model are reduced by using higher order polynomials. In addition, remaining error in the RS weight equation is characterized, and two error measures are introduced. One of the measures is qualitative, and it is used to identify regions of design space where RS accuracy may be poor. The second measure is quantitative, but conservative. Its use is demonstrated for incorporating the uncertainty due to RS weight equation with parameter uncertainty in order to compare competing designs for robustness.

Papila, Melih

44

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

45

Fatigue characteristics of ultra high molecular weight polyethylene with different molecular weight for implant material.  

PubMed

In order to investigate the effect of molecular weight on fatigue characteristics in the ultra high molecular weight polyethylene (UHMWPE), tension-tension fatigue tests of notched specimens were carried out in the present study. The effects of frequency and stress ratio on the fatigue characteristics were also investigated and fractography was discussed. The fatigue strength does not increase with increasing molecular weight. The fatigue strength might be influenced by the high degree of crystallinity in spite of the decreased tie molecule density in this study. Almost no effect of frequency on the number of cycles to failure can be observed. However, the higher the frequency, the higher the crack tip temperature. The effects of heat and strain rate on the fatigue strength must be considered in polymer materials. At a high stress ratio, the stress-number of cycles to failure (S-N) curves shift to high number cycles to failure side. Both stress amplitude and mean stress influence the fatigue life of UHMWPE. PMID:15348311

Niinomi, M; Wang, L; Enjitsu, T; Fukunaga, K

2001-03-01

46

Recovery of petroleum with chemically treated high molecular weight polymers  

SciTech Connect

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

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

1980-11-18

47

Molecular Weight Distribution of (Semi) Commercial Lignin Derivatives  

Microsoft Academic Search

Absolute molecular weights of several commercially and semi-commercially available lignins were determined by gel permeation chromatography (GPC with a differential viscosity detector (DV). Solubility in THF was assured by acetylation. Polystyrene molecular weight standards were used for establishing a universal calibration curve. The lignins included those from hardwood, softwood, and sugar cane bagasse; and these were isolated by the kraft

Wolfgang G. Glasser; Vipul Davé; Charles E. Frazier

1993-01-01

48

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

49

Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal-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 containing a carbide, nitride, boride or oxide of a Group I-A metal, under C/sub 2+/ hydrocarbon synthesis conditions such tat 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.

1986-07-08

50

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

51

Wear characteristics of ultrahigh molecular weight polyethylene (UHMWPE)  

NASA Astrophysics Data System (ADS)

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

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

2002-10-01

52

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

53

Liquid hydrocarbon fuels containing high molecular weight Mannich bases  

SciTech Connect

Reaction products obtained from the Mannich condensation of high molecular weight alkyl-substituted hydroxy aromatic compounds, amines and aldehydes provide improved detergency in liquid hydrocarbon fuels. Optionally, a non-volatile hydrocarbon carrier fluid may be included.

Udelhofen, J.H.; Watson, R.W.

1980-11-04

54

Hydrodynamic Characterization and Molecular Weight Estimation of Ultrasonically Sheared DNA.  

National Technical Information Service (NTIS)

The sedimentation coefficients and intrinsic viscosities of ultrasonically sheared calf thymus DNA have been determined. The molecular weight estimation according to these parameters have been compared with the ones obtained from the electrophoretic migra...

F. Garces J. I. Casal A. Garcia

1981-01-01

55

Further Investigations on the Molecular Weight of Staphylococcal Enterotoxin B.  

National Technical Information Service (NTIS)

The molecular weight of staphylococcal enterotoxin B was determined independently and by methods not previously applied to the protein; the results agree well with those obtained in two earlier studies. In order to check the previous determinations, analy...

D. Trkula R. L. Sine E. J. Schantz

1968-01-01

56

Ultra-High Molecular Weight Silphenylene-Siloxane Polymers.  

National Technical Information Service (NTIS)

Silphenylene-siloxane copolymers with molecular weights above one million were prepared using a two stage polymerization technique. The technique was successfully scaled up to produce 50 grams of this high polymer in a single run. The reactive monomer app...

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

1984-01-01

57

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

58

Treatment of venous thromboembolism with low-molecular-weight heparin  

Microsoft Academic Search

Summary There is now ample evidence to indicate that certain low-molecular-weight heparins given subcutaneously can replace continuous intravenous unfractionated heparin for the initial treatment of venous thromboembolism. The low-molecular-weight heparins have a predictably high absorption rate when given subcutaneously and a prolonged duration of action, permitting them to be given by a once or twice daily injection for the prevention

Russell D. Hull; Graham F. Pineo

1995-01-01

59

Molecular Weight Distribution of ?-Glucan in Oat-Based Foods  

Microsoft Academic Search

Cereal Chem. 81(3):356-360 Oats, different oat fractions as well as experimental and commercial oat-based foods, were extracted with hot water containing thermostable ?-amylase. Average molecular weight and molecular weight distributions of ?-glucan in extracts were analyzed with a calibrated high-performance size-exclusion chromatography system with Calcofluor detection, specific for the ?-glucan. Oats, rolled oats, oat bran, and oat bran concentrates all

Per Åman; Lena Rimsten; Roger Andersson

2004-01-01

60

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

SciTech Connect

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

Mickiewicz, Rafal A.; Ntoukas, Eleftherios; Avgeropoulos, Apostolos; Thomas, Edwin L. (MIT); (Ioannina)

2009-08-26

61

On high-order accurate weighted essentially non-oscillatory and discontinuous Galerkin schemes for compressible turbulence simulations.  

PubMed

In this article, we give a brief overview on high-order accurate shock capturing schemes with the aim of applications in compressible turbulence simulations. The emphasis is on the basic methodology and recent algorithm developments for two classes of high-order methods: the weighted essentially non-oscillatory and discontinuous Galerkin methods. PMID:23185054

Shu, Chi-Wang

2013-01-13

62

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

2010-01-01

63

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

2009-04-01

64

Dissolution of poly(p-hydroxystyrene): molecular weight effects  

NASA Astrophysics Data System (ADS)

In the present study, dissolution rates of PPHS films were measured in aqueous base solvents and in 4-methyl-2-pentanone (MIBK) using laser interferometry. Molecular weights from 6,000 to 100,000 were employed. The films (0.5 to 2 micrometers thick) were spun on silicon wafers from MIBK solutions and baked 1 hour at 160 degree(s)C. The most striking feature of dissolution behavior is the peculiar way in which rate varies with molecular weight. Below a molecular weight of about 20,000, the rate decreases with molecular weight as one might expect. Above 30,000, the rate in aqueous base is much higher and seems to be almost independent of molecular weight. The behavior in MIBK, while more conventional, shows some of the same features. Another feature found with PPHS that is not usual with other polymers is a decrease in dissolution rate with increased thickness. Conventional wisdom would predict that retained solvents (after baking) in thick films would accelerate dissolution compared to thin films. Moreover, the interferograms for thick films show no pronounced change in dissolution rate as the film dissolves. Baking conditions and the pH of the aqueous base developer also affect the dissolution behavior.

Long, Treva; Rodriguez, Ferdinand

1991-06-01

65

Is Accurate Perception of Body Image Associated with Appropriate Weight-Control Behavior among Adolescents of the Seychelles.  

PubMed

Background. We examined body image perception and its association with reported weight-control behavior among adolescents in the Seychelles. Methods. We conducted a school-based survey of 1432 students aging 11-17 years in the Seychelles. Perception of body image was assessed using both a closed-ended question (CEQ) and Stunkard's pictorial silhouettes (SPS). Voluntary attempts to change weight were also assessed. Results. A substantial proportion of the overweight students did not consider themselves as overweight (SPS: 24%, CEQ: 34%), and a substantial proportion of the normal-weight students considered themselves as too thin (SPS: 29%, CEQ: 15%). Logistic regression analysis showed that students with an accurate weight perception were more likely to have appropriate weight-control behavior. Conclusions. We found that substantial proportions of students had an inaccurate perception of their weight and that weight perception was associated with weight-control behavior. These findings point to forces that can drive the upwards overweight trends. PMID:21603277

Alwan, Heba; Viswanathan, Bharathi; Paccaud, Fred; Bovet, Pascal

2011-03-24

66

Inhibition of phagocytosis by high molecular weight hyaluronate.  

PubMed Central

The effect of sodium hyaluronate on phagocytosis was studied using a sensitive polystyrene latex sphere assay in mouse peritoneal macrophage monolayers. Viscous solutions of high molecular weight hyaluronate (4.6 X 10(5)--2.8 X 10(6)) caused a dose-dependent inhibition of phagocytosis, but low molecular weight hyaluronate (9.0 X 10(4)) was not inhibitory at equivalent viscosity. The inhibitory effect of high molecular weight hyaluronate did not appear to be mediated by the polyanionic charge of the molecule since sulphated glycosaminoglycans with greater charge density (heparin and chondroitin sulphate) were ineffective. In addition, competitive inhibition studies indicated that a direct effect on possible cell surface membrane receptors was unlikely. Instead, physical factors such as steric hindrance by the continuous polymeric network, were considered of more importance. Alternatively, the hydrophilic polysaccharide may have inhibited phagocytosis by providing an unsuitable surface for adhesive contact between the latex beads and the cell surface.

Forrester, J V; Balazs, E A

1980-01-01

67

Extraction of High Molecular Weight DNA from Microbial Mats  

PubMed Central

Successful and accurate analysis and interpretation of metagenomic data is dependent upon the efficient extraction of high-quality, high molecular weight (HMW) community DNA. However, environmental mat samples often pose difficulties to obtaining large concentrations of high-quality, HMW DNA. Hypersaline microbial mats contain high amounts of extracellular polymeric substances (EPS)1 and salts that may inhibit downstream applications of extracted DNA. Direct and harsh methods are often used in DNA extraction from refractory samples. These methods are typically used because the EPS in mats, an adhesive matrix, binds DNA2,3 during direct lysis. As a result of harsher extraction methods, DNA becomes fragmented into small sizes4,5,6. The DNA thus becomes inappropriate for large-insert vector cloning. In order to circumvent these limitations, we report an improved methodology to extract HMW DNA of good quality and quantity from hypersaline microbial mats. We employed an indirect method involving the separation of microbial cells from the background mat matrix through blending and differential centrifugation. A combination of mechanical and chemical procedures was used to extract and purify DNA from the extracted microbial cells. Our protocol yields approximately 2 ?g of HMW DNA (35-50 kb) per gram of mat sample, with an A260/280 ratio of 1.6. Furthermore, amplification of 16S rRNA genes7 suggests that the protocol is able to minimize or eliminate any inhibitory effects of contaminants. Our results provide an appropriate methodology for the extraction of HMW DNA from microbial mats for functional metagenomic studies and may be applicable to other environmental samples from which DNA extraction is challenging.

Bey, Benjamin S.; Fichot, Erin B.; Norman, R. Sean

2011-01-01

68

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

69

Low-molecular-weight post-translationally modified microcins  

Microsoft Academic Search

Summary Microcins are a class of ribosomally synthesized anti- bacterial peptides produced by Enterobacteriaceae and active against closely related bacterial species. While some microcins are active as unmodified peptides, others are heavily modified by dedicated maturation enzymes. Low-molecular-weight micro- cins from the post-translationally modified group target essential molecular machines inside the cells. In this review, available structural and functional data

Konstantin Severinov; Ekaterina Semenova; Alexey Kazakov; Teymur Kazakov; Mikhail S. Gelfand

2007-01-01

70

Accurate Initialization of Neural Network Weights by Backpropagation of the Desired Response  

Microsoft Academic Search

Abstracf - Proper initialization of neural networks is critical for a successful training of its weights. Many methods have been proposed to achieve this, including heuristic least squares approaches. In this paper, inspired by these previous attempts to train (or initialize) neural networks, we formulate a mathematically sound algorithm based on backpropagating the desired output through the layers of a

Deniz Erdogmus; Oscar Fontenla-Romero; Jose C. Principe; Amparo Alonso-Betanzos; Enrique Castillo; Robert Jenssen

2005-01-01

71

Accurate initialization of neural network weights by backpropagation of the desired response  

Microsoft Academic Search

Proper initialization of neural networks is critical for a successful training of its weights. Many methods have been proposed to achieve this, including heuristic least squares approaches. In this paper, inspired by these previous attempts to train (or initialize) neural networks, we formulate a mathematically sound algorithm based on backpropagating the desired output through the layers of a multilayer perceptron.

Deniz Erdogmus; Oscar Fontenla-Romero; Jose C. Principe; Amparo Alonso-Betanzos; Enrique Castillo; Robert Jenssen

2003-01-01

72

Mothers' and Fathers' Perceptions of Their Adolescent Daughters' Shape, Weight, and Body Esteem: Are They Accurate?  

ERIC Educational Resources Information Center

|Examined parents' awareness of their daughters' attitudes, beliefs, and feelings about their bodies. Sixty-six adolescent daughters completed an eating disorder scale, a body figure rating scale, and made ratings of their shape and weight. Greater discrepancies between parents' estimates of daughters' body esteem and daughters' self-reported body…

Geller, Josie; Srikameswaran, Suja; Zaitsoff, Shannon L.; Cockell, Sarah J.; Poole, Gary D.

2003-01-01

73

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

Code of Federal Regulations, 2013 CFR

...Superintendent of Documents, Government Printing Office, Washington...DC 20408. (b) All scales used to determine...replacements are made to a scale, it shall not be used...or a State or local government weights and measures...registered or licensed scale repair firm or...

2013-01-01

74

Surface phase separation between polythylene oxide of different molecular weight  

NASA Astrophysics Data System (ADS)

In-plane phase separation of polyelethylene oxide of different molecular weight has been observed. A systematic investigation on a broad range of Mw show that the process is originated from the conformatinal entropy for a polymer confined on a surface (thin film).

Chen, Rui; Yang, Jingfa; Zhao, Jiang

2013-03-01

75

Molecular Weights and Physical Properties of Deoxyribonucleic Acid  

Microsoft Academic Search

IN the measurements of the molecular weight from light scattering and of other physical properties of deoxyribonucleic acid, an extraordinary variety of results has been obtained1, even with samples prepared from a single source, namely, calf thymus. To some extent this might be accounted for as a result of fractionation of the material resulting from its physical heterogeneity, which has

J. A. V. Butler; D. J. R. Laurence; A. B. Robins; K. V. Shooter

1957-01-01

76

Molecular Weight Effects on the Viscoelastic Response of a Polyimide.  

National Technical Information Service (NTIS)

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 un...

L. M. Nicholson K. S. Whitley T. S. Gates

2000-01-01

77

Nylon 6 nanocomposites: the effect of matrix molecular weight  

Microsoft Academic Search

Organoclay nanocomposites based on three different molecular weight grades of nylon 6 were prepared by melt processing using a twin screw extruder. Mechanical properties, transmission electron microscopy, wide-angle X-ray diffraction, and rheological measurements were used to characterize the three types of composites. Tensile modulus and yield strength were found to increase with increasing concentration of clay, while elongation at break

T. D. Fornes; P. J. Yoon; H. Keskkula; D. R. Paul

2001-01-01

78

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

79

Ubiquitous occurrence of high molecular weight hydrocarbons in crude oils  

Microsoft Academic Search

For many years the presence of waxes in crude oils has been associated with organic matter derived from terrigenous sources. High temperature gas chromatography (HTGC) has been used to establish the ubiquitous presence of high molecular weight (HMW) hydrocarbons, extending as high as C120, in crude oils. HMW hydrocarbons (>C40+) have been observed in crude oils derived from terrigenous, lacustrine,

Michael Hsieh; R. Paul Philp

2001-01-01

80

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.

Braswell, Emory H.

1987-01-01

81

Thromboprophylaxis with Low Molecular Weight Heparin (Dalteparin) in Pregnancy  

Microsoft Academic Search

Venous thromboembolism remains an important cause of maternal mortality. For women at risk during pregnancy, the recommended venous thromboembolismprophylaxis is unfractionated heparin. Low molecular weight heparins, such as dalteparin, also may be suitable, but randomised trials have not been performed. Pregnant women (105) with confirmed previous or current thromboembolism were randomised to receive either unfractionated heparin twice daily (mean 20569

Ville Pettilä; Risto Kaaja; Pekka Leinonen; Ulla Ekblad; Matti Kataja; Eero Ikkala

1999-01-01

82

Diffusion of low molecular weight siloxane from bulk to surface  

Microsoft Academic Search

Silicone-based materials for outdoor insulators have the advantage that low molecular weight (LMW) components migrate through the material and coat the surface, thereby restoring hydrophobicity over a period of hours. By measuring the IR absorption of siloxane migrating to the silicone surface through a thin carbon coating, the time constant for migration was calculated. According to the time dependence of

H. Homma; T. Kuroyagi; K. Izumi; C. L. Mirley; J. Ronzello; S. A. Boggs

1999-01-01

83

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

84

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

85

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.

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

2009-01-01

86

Low-Molecular-Weight Heparin for Vertebral Artery Dissection  

Microsoft Academic Search

A case of vertebral artery dissection and consequent basilar artery thrombosis in a 6-year-old patient is reported. The patient was treated with subcutaneous low-molecular-weight heparin at therapeutic doses (enoxaparin, 100 IU\\/kg twice daily) for 3 weeks, then reduced to 2,000 IU\\/day for 3 more weeks. After this time a magnetic resonance angiogram was obtained that showed complete recanalization of the

Marco Marietta; Marcello Bertesi; Nino Rozzi; Maria Carmen Cano; Stefano Vallone; Cinzia Cappi; Samantha Pozzi; Giuseppe Torelli

2002-01-01

87

Low molecular weight MPEG-assisted organic synthesis.  

PubMed

A toolkit of low molecular weight MPEG-supported coupling agents ((M)IIDQ, (M)EDCI), reagents for the Mitsunobu reaction ((M)DEAD, (M)TPP), an alternative to diazomethane, and scavengers can be used in the solution-phase synthesis of amides, esters and ureas and are easily removed after use by solid-phase extraction (MSPE) using normal silica. PMID:20473429

Figlus, Marek; Tarruella, Albert C; Messer, Anastasia; Sollis, Steven L; Hartley, Richard C

2010-05-14

88

A low-molecular-weight angiogenic factor in cat retina.  

PubMed Central

A low-molecular-weight angiogenic factor has been isolated from healthy adult cat retinas. The factor, which has been purified by diethylaminoethyl (DEAE) cellulose chromatography and affinity chromatography, stimulates neovascularisation of the chick chorioallantoic membrane and has a number of properties similar to those previously described for a tumour factor. The finding of an angiogenic factor in healthy retina and its relationship to previously described inhibitors of angiogenesis is discussed. Images

Kissun, R D; Hill, C R; Garner, A; Phillips, P; Kumar, S; Weiss, J B

1982-01-01

89

Antioxidative activity of chitosans with varying molecular weights  

Microsoft Academic Search

Antioxidant activity of chitosans of different molecular weights (30, 90 and 120kDa chitosan) in salmon (Salmo salar) was investigated. The progress of oxidation was monitored by employing the 2-thiobarbituric acid-reactive substances (TBARS) and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assays. In general, all chitosans exhibited antioxidative activities in salmon. The addition of chitosans to salmon reduced lipid oxidation for seven days of

Kyung W. Kim; R. L. Thomas

2007-01-01

90

Wear characteristics of ultrahigh molecular weight polyethylene (UHMWPE)  

Microsoft Academic Search

The wear of ultrahigh molecular weight polyethylene (UHMWPE) bearing against 316 stainless steel or cobalt chromium (Co-Cr)\\u000a alloy was measured using a 12-channel wear tester especially developed for the evaluation of candidate materials for prosthetic\\u000a joints. The coefficient of friction and wear rate were determined as a function of lubricant, contact stress, and metallic\\u000a surface roughness in tests lasting 2–3

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

2002-01-01

91

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

SciTech Connect

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

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

1980-01-01

92

Buckling in polymer monolayers: Molecular-weight dependence  

NASA Astrophysics Data System (ADS)

We present systematic investigations of buckling in Langmuir monolayers of polyvinyl acetate formed at the air-water interface. On compression the polymer monolayers are converted to a continuous membrane with a thickness of ˜2-3nm of well-defined periodicity, ?b . Above a certain surface concentration the membrane undergoes a morphological transition buckling, leading to the formation of striped patterns. The periodicity seems to depend on molecular weight as per the predictions of the gravity-bending buckling formalism of Milner for fluidlike films on water. However anomalously low values of bending rigidity and Young’s modulus are obtained using this formalism. Hence we have considered an alternative model of buckling-based solidlike films on viscoelastic substrates. The values of bending rigidity and Young’s modulus obtained by this method, although lower than expected, are closer to the bulk values. Remarkably, no buckling is found to occur above a certain molecular weight. We have tried to explain the observed molecular-weight dependence in terms of the variation in isothermal compressive modulus of the monolayers with surface concentration as well as provided possible explanations for the obtained low values of mechanical properties similar to that observed for ultrathin polymer films.

Srivastava, S.; Basu, J. K.

2009-04-01

93

Antioxidant acitivity of low molecular weight hyaluronic acid.  

PubMed

Two polysaccharides, low molecular weight hyaluronic acid-1 (LMWHA-1) and LMWHA-2, with their molecular weight of 1.45×10(5) and 4.52×10(4)Da, respectively, were prepared from high molecular weight hyaluronic acid (HA,1.05×10(6)Da). LMWHA-1, LMWHA-2 and HA were studied for their antioxidant activities. In vitro antioxidant assay, LMWHA showed strong inhibition of lipid peroxidation and scavenging activities of hydroxyl radical, moderate 1,1-diphenyl-2-picryldydrazyl radical and superoxide anion scavenging activity. In addition, the LMWHA-1 exhibited much stronger antioxidant activity than LMWHA-2 and HA. For antioxidant testing in vivo, LMWHA-1, LMWHA-2 and HA were orally administrated over a period of 7days in a cyclophosphamide(CY) induced immunosuppressed mice model. As results, administration of LMWHA was able to overcome CY-induced immunosuppression and significantly raised the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and total antioxidant capacity (TAOC) in immunosuppressed mice. The results showed that the LMWHA, possessing pronounced free radical scavenging and antioxidant activities. PMID:21787831

Ke, Chunlin; Sun, Lanping; Qiao, Deliang; Wang, Di; Zeng, Xiaoxiong

2011-07-20

94

Buckling in polymer monolayers: Molecular-weight dependence  

SciTech Connect

We present systematic investigations of buckling in Langmuir monolayers of polyvinyl acetate formed at the air-water interface. On compression the polymer monolayers are converted to a continuous membrane with a thickness of {approx}2-3 nm of well-defined periodicity, {lambda}{sub b}. Above a certain surface concentration the membrane undergoes a morphological transition buckling, leading to the formation of striped patterns. The periodicity seems to depend on molecular weight as per the predictions of the gravity-bending buckling formalism of Milner et al. for fluidlike films on water. However anomalously low values of bending rigidity and Young's modulus are obtained using this formalism. Hence we have considered an alternative model of buckling-based solidlike films on viscoelastic substrates. The values of bending rigidity and Young's modulus obtained by this method, although lower than expected, are closer to the bulk values. Remarkably, no buckling is found to occur above a certain molecular weight. We have tried to explain the observed molecular-weight dependence in terms of the variation in isothermal compressive modulus of the monolayers with surface concentration as well as provided possible explanations for the obtained low values of mechanical properties similar to that observed for ultrathin polymer films.

Srivastava, S.; Basu, J.K.; (IIS)

2010-11-12

95

Buckling in polymer monolayers: molecular-weight dependence.  

PubMed

We present systematic investigations of buckling in Langmuir monolayers of polyvinyl acetate formed at the air-water interface. On compression the polymer monolayers are converted to a continuous membrane with a thickness of approximately 2-3 nm of well-defined periodicity, lambdab. Above a certain surface concentration the membrane undergoes a morphological transition buckling, leading to the formation of striped patterns. The periodicity seems to depend on molecular weight as per the predictions of the gravity-bending buckling formalism of Milner for fluidlike films on water. However anomalously low values of bending rigidity and Young's modulus are obtained using this formalism. Hence we have considered an alternative model of buckling-based solidlike films on viscoelastic substrates. The values of bending rigidity and Young's modulus obtained by this method, although lower than expected, are closer to the bulk values. Remarkably, no buckling is found to occur above a certain molecular weight. We have tried to explain the observed molecular-weight dependence in terms of the variation in isothermal compressive modulus of the monolayers with surface concentration as well as provided possible explanations for the obtained low values of mechanical properties similar to that observed for ultrathin polymer films. PMID:19518241

Srivastava, S; Basu, J K

2009-04-17

96

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

PubMed

Dietary fiber and its quantitation in foods have been of significant interest in the nutrition community for over 50 years. A number of AOAC Official Methods of Analysis have been adopted for the analysis of dietary fiber and some of its fractions and components commensurate with the evolving discoveries of dietary fiber nutrition research. Quantitation of low-molecular-weight soluble dietary fiber (LMWSDF) has been difficult due to high solubility in a precipitating solvent mixture of four parts alcohol and one part water. AOAC Method 2001.03 effectively quantitates LWMSDF subsequent to gravimetric removal of high-molecular-weight dietary fiber using LC. However, deionization and concentration of the enzymatic digestate, necessary to assure accurate LC quantitation, requires substantial time and manual labor. A modification to the method and resulting method performance is presented that describes a means of simultaneously deionizing the digestate and quantitating the LMWSDF in a single LC injection, eliminating a number of time-consuming manual preparation steps. PMID:20334185

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

97

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

PubMed

Proteins are usually identified by their molecular weights, and atomic force microscopy (AFM) produces images of single molecules in three dimensions. We have used AFM to measure the molecular volumes of a number of proteins and to determine any correlation with their known molecular weights. We used native proteins (the TATA-binding protein Tbp, a fusion protein of glutathione-S-transferase and the renal potassium channel protein ROMK1, the immunoglobulins IgG and IgM, and the vasodilator-stimulated phosphoprotein VASP) and also denatured proteins (the red blood cell proteins actin, Band 3 and spectrin separated by SDS-gel electrophoresis and isolated from nitrocellulose). Proteins studied had molecular weights between 38 and 900 kDa and were imaged attached to a mica substrate. We found that molecular weight increased with an increasing molecular volume (correlation coefficient = 0.994). Thus, the molecular volumes measured with AFM compare well with the calculated volumes of the individual proteins. The degree of resolution achieved (lateral 5 nm, vertical 0.2 nm) depended upon the firm attachment of the proteins to the mica. This was aided by coating the mica with suitable detergent and by imaging using the AFM tapping mode which minimizes any lateral force applied to the protein. We conclude that single (native and denatured) proteins can be imaged by AFM in three dimensions and identified by their specific molecular volumes. This new approach permits detection of the number of monomers of a homomultimeric protein and study of single proteins under physiological conditions at the molecular level. PMID:9426291

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

1998-02-01

98

Determination of molecular weights by differential cryoscopy on small volumes of dilute solutions of oligopeptides.  

PubMed

A differential cryoscope of the equilibrium type is described. It requires only 1 ml of sample for a molecular-weight determination of a solute in a solvent that freezes below room temperature. The instrument is sensitive to +/- 0.0002 degrees C, which corresponds to +/- 0.0001 mol of solute per 1000 g of water. The apparatus was evaluated by measuring the freezing point depressions of 0.015 M urea and 0.01 M alanine in water, the measured molecular weights being accurate to within +/- 5%. The molecular weights of the following oligopeptides were then measured to determine their states of aggregation in the cited solvents: Ac-Asn-Pro-Tyr-NHMe in H2O and dimethyl sulfoxide and cyclo(L-alanyl-L-alanyl-epsilon-aminocaproyl), cyclo(L-alanyl-D-alanyl-epsilon-aminocaproyl), cyclo(L-alanyl-L-analyl-omega-capryl), cyclo(L-alanyl-D-alanyl-omega-capryl), and Ac-Tyr-Pro-Asn-NHMe in dimethyl sulfoxide. PMID:6528976

Davenport, V G; Stimson, E R; Scheraga, H A

1984-11-01

99

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

100

The Influence of molecular weight on nanoporous polymer films  

NASA Astrophysics Data System (ADS)

Asymmetric diblock copolymers of poly(styrene) and poly(methyl methacrylate), P(S-b-MMA), having cylindrical domains of PMMA, provide a model system to produce nanoporous thin films. Using either controlling interfacial interaction or applying an external electric field, cylinder domains can be oriented normal to the surface. Exposing the film to deep UV radiation may degrade the PMMA and crosslink the styrene matrix. After washing a porous film is obtained. By changing the molecular weight, smooth porous films with pore diameters ranging from 13 to 50nm are obtained where the pores are closely hexagonal packed.

Xu, Ting; Kim, Ho-Cheol; Derouchey, Jason; Seney, Chevey; Levesque, Cathy; Martin, Paul; Stafford, Chris; Russell, Thomas

2001-03-01

101

Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases  

NASA Astrophysics Data System (ADS)

We present a library of Gaussian basis sets that has been specifically optimized to perform accurate molecular calculations based on density functional theory. It targets a wide range of chemical environments, including the gas phase, interfaces, and the condensed phase. These generally contracted basis sets, which include diffuse primitives, are obtained minimizing a linear combination of the total energy and the condition number of the overlap matrix for a set of molecules with respect to the exponents and contraction coefficients of the full basis. Typically, for a given accuracy in the total energy, significantly fewer basis functions are needed in this scheme than in the usual split valence scheme, leading to a speedup for systems where the computational cost is dominated by diagonalization. More importantly, binding energies of hydrogen bonded complexes are of similar quality as the ones obtained with augmented basis sets, i.e., have a small (down to 0.2 kcal/mol) basis set superposition error, and the monomers have dipoles within 0.1 D of the basis set limit. However, contrary to typical augmented basis sets, there are no near linear dependencies in the basis, so that the overlap matrix is always well conditioned, also, in the condensed phase. The basis can therefore be used in first principles molecular dynamics simulations and is well suited for linear scaling calculations.

Vandevondele, Joost; Hutter, Jürg

2007-09-01

102

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

103

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

104

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

105

Multiscale investigation of low molecular weight glass formers  

NASA Astrophysics Data System (ADS)

Ortho-terphenyl (OTP), a very well known and well investigated organic glass former, is used as a model to study the static and dynamic properties of low molecular weight glass formers. Molecular dynamics is applied to simulate 800 molecules in atomistic detail. The model is able to provide very good agreement with experimental observations. Our simulation gives the glass transition temperature (˜260K) slightly higher than the experimental value (243K) but is much closer to that value than comparable simulations. Radial distribution functions calculated at temperatures above and below the glass transition temperature show that there are no remarkable changes in structure at the molecular level. We study the in-homogeneity at the local level around each molecule and compare static and dynamic heterogeneities. From the radial distribution functions we develop a structural coarse grained model. With this coarser model in which each ring of OTP is considered as one super atom, OTP should provide similar structural and dynamic properties above and below glass transition temperature. Future work on this multiscale approach includes applying the Density of States Monte Carlo technique to this real glass forming organic molecule. This novel Monte Carlo technique has been used for a binary Lennard Jones mixture as model glass former. This would be the first approach to apply it to a real glass forming liquid. We will eventually be able to study the effect of confinement on the transition.

Ghosh, Jayeeta

2005-03-01

106

Characterization of high molecular weight polyethylenes using high temperature asymmetrical flow field-flow fractionation with on-line infrared, light scattering, and viscometry detection  

Microsoft Academic Search

High temperature asymmetrical flow field-flow fractionation (HTAF4) coupled to infrared (IR), multi-angle light scattering (MALS), and viscometry (Visc) detection is introduced as a tool for the characterization of high molecular weight polyethylenes. The high molecular weight fraction strongly affects the rheological behaviour and processability of polyethylene materials and can often not be accurately resolved by current technology such as high

E. P. C. Mes; H. de Jonge; T. Klein; R. R. Welz; D. T. Gillespie

2007-01-01

107

Accurate Molecular Classification of Renal Tumors Using MicroRNA Expression  

PubMed Central

Subtypes of renal tumors have different genetic backgrounds, prognoses, and responses to surgical and medical treatment, and their differential diagnosis is a frequent challenge for pathologists. New biomarkers can help improve the diagnosis and hence the management of renal cancer patients. We extracted RNA from 71 formalin-fixed paraffin-embedded (FFPE) renal tumor samples and measured expression of more than 900 microRNAs using custom microarrays. Clustering revealed similarity in microRNA expression between oncocytoma and chromophobe subtypes as well as between conventional (clear-cell) and papillary tumors. By basing a classification algorithm on this structure, we followed inherent biological correlations and could achieve accurate classification using few microRNAs markers. We defined a two-step decision-tree classifier that uses expression levels of six microRNAs: the first step uses expression levels of hsa-miR-210 and hsa-miR-221 to distinguish between the two pairs of subtypes; the second step uses either hsa-miR-200c with hsa-miR-139-5p to identify oncocytoma from chromophobe, or hsa-miR-31 with hsa-miR-126 to identify conventional from papillary tumors. The classifier was tested on an independent set of FFPE tumor samples from 54 additional patients, and identified correctly 93% of the cases. Validation on qRT-PCR platform demonstrated high correlation with microarray results and accurate classification. MicroRNA expression profiling is a very effective molecular bioassay for classification of renal tumors and can offer a quantitative standardized complement to current methods of tumor classification.

Fridman, Eddie; Dotan, Zohar; Barshack, Iris; David, Miriam Ben; Dov, Avital; Tabak, Sarit; Zion, Orit; Benjamin, Sima; Benjamin, Hila; Kuker, Hagit; Avivi, Camila; Rosenblatt, Kinneret; Polak-Charcon, Sylvie; Ramon, Jacob; Rosenfeld, Nitzan; Spector, Yael

2010-01-01

108

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

109

Chemoenzymatic Synthesis of Homogeneous Ultralow Molecular Weight Heparins  

PubMed Central

Ultralow molecular weight (ULMW) heparins are sulfated glycans that are clinically used to treat thrombotic disorders. ULMW heparins range from 1500 to 3000 daltons, corresponding from 5 to 10 saccharide units. The commercial drug Arixtra (fondaparinux sodium) is a structurally homogeneous ULMW heparin pentasaccharide that is synthesized through a lengthy chemical process. Here, we report 10- and 12-step chemoenzymatic syntheses of two structurally homogeneous ULMW heparins (MW = 1778.5 and 1816.5) in 45 and 37% overall yield, respectively, starting from a simple disaccharide. These ULMW heparins display excellent in vitro anticoagulant activity and comparable pharmacokinetic properties to Arixtra, as demonstrated in a rabbit model. The chemoenzymatic approach is scalable and shows promise for a more efficient route to synthesize this important class of medicinal agent.

Xu, Yongmei; Masuko, Sayaka; Takieddin, Majde; Xu, Haoming; Liu, Renpeng; Jing, Juliana; Mousa, Shaker A.; Linhardt, Robert J.; Liu, Jian

2012-01-01

110

Chemoenzymatic synthesis of homogeneous ultralow molecular weight heparins.  

PubMed

Ultralow molecular weight (ULMW) heparins are sulfated glycans that are clinically used to treat thrombotic disorders. ULMW heparins range from 1500 to 3000 daltons, corresponding from 5 to 10 saccharide units. The commercial drug Arixtra (fondaparinux sodium) is a structurally homogeneous ULMW heparin pentasaccharide that is synthesized through a lengthy chemical process. Here, we report 10- and 12-step chemoenzymatic syntheses of two structurally homogeneous ULMW heparins (MW = 1778.5 and 1816.5) in 45 and 37% overall yield, respectively, starting from a simple disaccharide. These ULMW heparins display excellent in vitro anticoagulant activity and comparable pharmacokinetic properties to Arixtra, as demonstrated in a rabbit model. The chemoenzymatic approach is scalable and shows promise for a more efficient route to synthesize this important class of medicinal agent. PMID:22034431

Xu, Yongmei; Masuko, Sayaka; Takieddin, Majde; Xu, Haoming; Liu, Renpeng; Jing, Juliana; Mousa, Shaker A; Linhardt, Robert J; Liu, Jian

2011-10-28

111

Lipid solubility and molecular weight: whose idea was that.  

PubMed

Gene Cooper was a bright theoretician, a skilled product developer, and a motivational leader who applied his talents to the skin science area early in his career. His work led to the development of finite dose skin absorption models, chemical penetration enhancer technologies and quantitative structure-penetration relationships for chemicals contacting human skin. His ideas regarding the impact of molecular weight and lipid solubility on skin transport catalyzed the later development by Potts and Guy of the first successful skin permeability model. But Gene's most important contribution to the field was as a scientific role model and an inspirational leader who launched the careers of several young scientists, including the author of this article. PMID:23921116

Kasting, G B

2013-07-29

112

Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities  

SciTech Connect

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

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

2000-07-14

113

Starburst low-molecular weight polyethylenimine for efficient gene delivery.  

PubMed

Low-molecular weight polyethylenimine (LMW PEI) shows the advantage of low-cytotoxicity, but has been inefficient in gene delivery as a consequence of the low-charge density. A number of previous studies employed the approach of crosslinking to solve this problem. In this study, a starburst LMW PEI gene vector has been developed. It has a polyamidoamine (PAMAM) core conjugated with a shell composed of LWM PEI and polyethylene glycol (PEG), that is PAMAM-PEI-PEG. Plasmid DNA (pEGFP-N1) and human cervix epithelial carcinoma (HeLa) cells were used in the study. The results showed that the starburst LMW PEI could effectively condense DNA at N/P above 5. The polyplexes had a size of about 500 nm and a nearly neutral surface because of the PEG shielding effect. This novel gene vector is able to maintain the low-cytotoxicity of LMW PEI, whereas its transfection efficiency was significantly improved. PMID:21997931

Zhao, Yanjun; Yang, Rulei; Liu, Dong; Sun, Mingjing; Zhou, Lijun; Wang, Zheng; Wan, Ying

2011-10-14

114

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

115

Structure and properties of low molecular weight amphiphilic peptide hydrogelators.  

PubMed

The search for low molecular weight hydrogelators (LMWH) with varying structural motif is getting intense because of its potential application in the field of biomedicines as well as the diversified area of nano-biotechnology. In this paper, we have developed hydrogels of simple cationic dipeptide amphiphiles that have a wide range of minimum gelation concentration (MGC), 12-0.25% (w/v) in plain water. The self-aggregation behavior of these thermoreversible hydrogelators has been investigated through different spectroscopic and microscopic techniques. A balanced participation of hydrophilicity and hydrophobicity is the major driving force for gelation, which could be modulated by a minute change in the architecture of the amphiphile head. The prospective use of this material in controlled release suggests that this system could also be applied as the drug delivery vehicle. Moreover, the presence of a biodegradable amide linkage susceptible to base or enzyme-catalyzed hydrolysis increases its probable applications as biomaterials. PMID:18052148

Mitra, Rajendra Narayan; Das, Debapratim; Roy, Sangita; Das, Prasanta Kumar

2007-12-04

116

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

117

Dairy Wastewater Treatment Using Low Molecular Weight Crab Shell Chitosan  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

118

High molecular weight kininogen is an inhibitor of platelet calpain.  

PubMed Central

Recent studies from our laboratory indicate that a high concentration of platelet-derived calcium-activated cysteine protease (calpain) can cleave high molecular weight kininogen (HMWK). On immunodiffusion and immunoblot, antiserum directed to the heavy chain of HMWK showed immunochemical identity with alpha-cysteine protease inhibitor--a major plasma inhibitor of tissue calpains. Studies were then initiated to determine whether purified or plasma HMWK was also an inhibitor of platelet calpain. Purified alpha-cysteine protease inhibitor, alpha-2-macroglobulin, as well as purified heavy chain of HMWK or HMWK itself inhibited purified platelet calpain. Kinetic analysis revealed that HMWK inhibited platelet calpain noncompetitively (Ki approximately equal to 5 nM). Incubation of platelet calpain with HMWK, alpha-2-macroglobulin, purified heavy chain of HMWK, or purified alpha-cysteine protease inhibitor under similar conditions resulted in an IC50 of 36, 500, 700, and 1,700 nM, respectively. The contribution of these proteins in plasma towards the inhibition of platelet calpain was investigated next. Normal plasma contained a protein that conferred a five to sixfold greater IC50 of purified platelet calpain than plasma deficient in either HMWK or total kininogen. Reconstitution of total kininogen deficient plasma with purified HMWK to normal levels (0.67 microM) completely corrected the subnormal inhibitory activity. However, reconstitution of HMWK deficient plasma to normal levels of low molecular weight kininogen (2.4 microM) did not fully correct the subnormal calpain inhibitory capacity of this plasma. These studies indicate that HMWK is a potent inhibitor as well as a substrate of platelet calpain and that the plasma and cellular kininogens may function as regulators of cytosolic, calcium-activated cysteine proteases. Images

Schmaier, A H; Bradford, H; Silver, L D; Farber, A; Scott, C F; Schutsky, D; Colman, R W

1986-01-01

119

Phosphorylation of a high molecular weight DNA polymerase. cap alpha  

SciTech Connect

Anti-human DNA polymerase ..cap alpha.. murine IgG SJK-287-38 neutralized DNA polymerase ..cap alpha.. activity from rat embryonic fibroblasts infected with a temperature-sensitive transformation mutant of Rous sarcoma virus (tsLA24). After centrifugation of a crude cytosol fraction from log-phase cells in a 5-20% linear sucrose gradient, polypeptides of M/sub r/ approx. 185,000 and 220,000 were immunoprecipitated only from gradient fractions containing DNA polymerase ..cap alpha.. activity. When similar cultures were incubated in medium containing (/sup 32/P)orthophosphate, it was found that the M/sub r/ 220,000 protein was phosphorylated but that the other peptides specific for polymerase ..cap alpha.. activity did not contain detectable amounts of phosphate. Phospho amino acid analysis of the high molecular weight immunoprecipitable proteins indicated that the labeled amino acid was phosphoserine. Incubation of 2.5 units of crude DNA polymerase ..cap alpha.. with 4 units of agarose-immobilized alkaline phosphatase resulted in a nearly complete inhibition of DNA polymerase ..cap alpha.. activity. Subsequent incubation of this preparation with 5 or 50 ..mu..M ATP, but not the nonhydrolyzable analog adenosine 5'-(..gamma..-thio)triphosphate, restored the in vitro DNA polymerizing activity. These results demonstrate that a high molecular weight DNA polymerase ..cap alpha.. is phosphorylated in cultured cells and that this protein is a substrate for a serine kinase rather than the tyrosine-specific protein kinase of Rous sarcoma virus. The results suggest that phosphorylation/dephosphorylation reactions modulate the activity of this polymerase.

Donaldson, R.W.; Gerner, E.W.

1987-02-01

120

Molecular Weight Dependence of Crystal Growth Rate and Its Corresponding States  

NASA Astrophysics Data System (ADS)

Poly(ethylene succinate) (PESU) was crystallized from the melt at a wide range of crystallization temperature. The paper will discuss on molecular weight dependent of spherulite growth rate. PESU was fractionated by GPC method. The fractionated molecular weight (Mp) was in the range of 1,000-10,000. PESU was isothermally crystallized on a slide glass at various temperatures from the melt. Each fractionated sample showed the maximum growth rate (Gmax). The Gmax increased with a decrease in molecular weight up to a certain molecular weight (Mp*=ca. 3,000) and then decreased with a decrease in molecular weight (below Mp*). When the growth rates and crystallization temperatures were normalized with the maximum growth rate and its temperature, a single master curve was observed. The universal plot indicates that the ratio of Go/Gmax shows constant. The molecular weight dependence of growth rate is only associated with Go and Gmax. In the region of molecular weight above Mp*, Log(Gmax) showed a linear relation to Log(Mp) and its slope was about -0.5. On the other hand below Mp*, the molecular weight dependence showed a positive slope of 1. The value of Mp* was coincided with a critical molecular weight of transition from ECC to FCC. The molecular weight dependence will be discussed on the basis of molecular adsorption and its diffusion mechanism on the crystal growing surface.

Okui, Norimasa

2001-03-01

121

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.

Fusti-Molnar, Laszlo; Merz, Kenneth M.

2008-01-01

122

A survey of factors contributing to accurate theoretical predictions of atomization energies and molecular structures  

NASA Astrophysics Data System (ADS)

High level electronic structure predictions of thermochemical properties and molecular structure are capable of accuracy rivaling the very best experimental measurements as a result of rapid advances in hardware, software, and methodology. Despite the progress, real world limitations require practical approaches designed for handling general chemical systems that rely on composite strategies in which a single, intractable calculation is replaced by a series of smaller calculations. As typically implemented, these approaches produce a final, or ``best,'' estimate that is constructed from one major component, fine-tuned by multiple corrections that are assumed to be additive. Though individually much smaller than the original, unmanageable computational problem, these corrections are nonetheless extremely costly. This study presents a survey of the widely varying magnitude of the most important components contributing to the atomization energies and structures of 106 small molecules. It combines large Gaussian basis sets and coupled cluster theory up to quadruple excitations for all systems. In selected cases, the effects of quintuple excitations and/or full configuration interaction were also considered. The availability of reliable experimental data for most of the molecules permits an expanded statistical analysis of the accuracy of the approach. In cases where reliable experimental information is currently unavailable, the present results are expected to provide some of the most accurate benchmark values available.

Feller, David; Peterson, Kirk A.; Dixon, David A.

2008-11-01

123

Human neutrophils contain and bind high molecular weight kininogen.  

PubMed Central

Because plasma kallikrein activates human neutrophils, and in plasma prekallikrein (PK) circulates complexed with high molecular weight kininogen (HMWK), we determined whether HMWK could mediate kallikrein's association with neutrophils. HMWK antigen (237 +/- 61 ng HMWK/10(8) neutrophils) was present in lysates of washed human neutrophils. Little if any plasma HMWK was tightly bound and nonexchangeable with the neutrophil surface. Human neutrophils were found to possess surface membrane-binding sites for HMWK but no internalization was detected at 37 degrees C. 125I-HMWK binding to neutrophils was dependent upon Zn2+. Binding of 125I-HMWK to neutrophils was specific and 90% reversible. 125I-HMWK binding to neutrophils was saturable with an apparent Kd of 9-18 nM and 40,000-70,000 sites per cell. Upon binding to neutrophils, 125I-HMWK was proteolyzed by human neutrophil elastase (HNE) into lower relative molecular mass derivatives. Furthermore, HMWK found in neutrophils also served as a cofactor for HNE secretion because neutrophils deficient in HMWK have reduced HNE secretion when stimulated in plasma deficient in HMWK or with purified kallikrein. These studies indicate that human neutrophils contain a binding site for HMWK that could serve to localize plasma or neutrophil HMWK on their surface to possibly serve as a receptor for kallikrein and to participate in HNE secretion by this enzyme. Images

Gustafson, E J; Schmaier, A H; Wachtfogel, Y T; Kaufman, N; Kucich, U; Colman, R W

1989-01-01

124

Correlation between antitumor activity, molecular weight, and conformation of lentinan.  

PubMed

A (1-->3)-beta-D-glucan having (1-->6) branching (L-FV-IB) from Lentinus edodes in water was degraded into seven fractions of different molecular weights by ultrasonic irradiation, and each was further fractionated into three parts, by precipitation from water into acetone at room temperature. The weight-average molecular weight (M(w)), radius of gyration ((z)(1/2)), and intrinsic viscosity ([eta]) of lentinan and its fractions in 0.9% NaCl aqueous solution and dimethyl sulfoxide (Me(2)SO) were determined by size-exclusion chromatography combined with multi-angle laser light scattering (SEC-LLS), LLS, and viscometry. Analysis of M(w), [eta], and (z)(1/2) in terms of known theory for worm-like chains yielded 2240 +/- 100 nm(-1), and 100 +/- 10 nm for molar mass per unit contour length (M(L)), and persistence length (q), respectively, corresponding with theoretical data for triple-helical chains. The [alpha](D) of lentinan in water-Me(2)SO mixtures indicated an order-disorder transition. The results indicated that lentinan exists as a triple helix in 0.9% NaCl aqueous solution and as a single flexible chain in Me(2)SO. Assays in vivo and in vitro against the growth of Sarcoma 180 solid tumor as well as the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method for lentinan showed that the triple-helix sample exhibited a relatively high inhibition ratio. Interestingly, the triple-helix lentinan with M(w) of 1.49 x 10(6) exhibited the highest antitumor activity in vivo, having an inhibition ratio (xi) of 49.5%, close to that of 5-fluorouracil (xi = 50.5%), whereas the bioactivity (xi = 12.3%) of its single flexible chains almost disappeared. The triple-helix conformation plays an important role in enhancing the antitumor effects of lentinan. PMID:15882854

Zhang, Lina; Li, Xuelian; Xu, Xiaojuan; Zeng, Fanbo

2005-06-13

125

Molecular weight averages as criteria for quality assessment of heated oils and fats  

Microsoft Academic Search

A simple method for quality assessment of heated oils and fats is described. The proposed method involves precise determination\\u000a of molecular weight averages (MWA)viz., the weight average molecular weight (\\u000a $$\\\\left( {\\\\bar {\\\\rm M}w} \\\\right)$$\\u000a ), the number average molecular weight (\\u000a $$\\\\left( {\\\\bar {\\\\rm M}n} \\\\right)$$\\u000a ) and the Z-average molecular weight (\\u000a $$\\\\left( {\\\\bar {\\\\rm M}z} \\\\right)$$\\u000a )

Sajid Husain; G. S. R. Sastry; N. Prasada Raju

1991-01-01

126

Determination of critical molecular weight for entangled macromolecules using the tensile strength data  

Microsoft Academic Search

The multivariable power dependence of polymer properties on molecular characteristics (Dobkowski, 1981) has been applied to molecular weight dependence of tensile strength, and the known equation of Flory (1945) has been extended taking polydispersity of polymers into account. Constant parameters of the relevant regression equations have been calculated using experimental data on tensile strength and molecular weight averagesMn andMw of

Zbigniew Dobkowski

1995-01-01

127

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

Microsoft Academic Search

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

James A. Davis; Rolf Gloor

1981-01-01

128

Measurement of low molecular weight silicon AMC to protect UV optics in photo-lithography environments  

NASA Astrophysics Data System (ADS)

A new analytical method for semiconductor-specific applications is presented for the accurate measurement of low molecular weight, silicon-containing, organic compounds TMS, HMDSO and D3. Low molecular weight / low boiling point silicon-containing compounds are not captured for extended periods of time by traditional chemical filters but have the same potential to degrade exposure tool optical surfaces as their high molecular weight counterparts. Likewise, we show that capturing these compounds on sample traps that are commonly used for organic AMC analysis does not work for various reasons. Using the analytical method described here, TMS, HMDSO and D3 can be measured artifact-free, with at least a 50:1 peak-to-noise ratio at the method detection limit, determined through the Hubaux-Vos method and satisfying a conservative 99% statistical confidence. Method detection limits for the compounds are 1-6 ppt in air. We present calibration curve, capacity, capture efficiency, break-through and repeatability data to demonstrate robustness of method. Seventy-one real-world samples from 26 projects taken in several fab environments show that TMS is found in concentrations 100 times higher than those of HMDSO and D3. All compounds are found in all environments in concentrations ranging from zero to 12 ppm, but most concentrations were below 50 ppb. All compounds are noticeably higher in litho-bays than in sub-fabs and we found all three compounds inside of two exposure tools, suggesting cleanroom and/or tool-internal contamination sources.

Lobert, Jürgen M.; Miller, Charles M.; Grayfer, Anatoly; Tivin, Anne M.

2009-03-01

129

Accurate staging of axillary lymph nodes from breast cancer patients using a novel molecular method  

PubMed Central

Background: The one-step nucleic acid amplification (OSNA) assay is a molecular-based lymph-node metastasis detection procedure that can assess a whole node and yields semi-quantitative results for the detection of clinically relevant nodal metastases. We aimed to determine the performance of the OSNA assay as an accurate nodal staging tool in comparison with routine histological examination. Methods: Subjects comprised 183 consecutive patients with pT1-2 breast cancer who underwent axillary dissection after positive sentinel-node (SN) biopsy with the OSNA assay. Of these, for non-SN evaluation, 119 patients underwent OSNA assay evaluation, whereas 64 had single-section histology. We compared the detection rates of non-SN metastasis and upstaging rates from the SN stage according to the American Joint Committee on Cancer staging between the OSNA and histology cohorts. Results: OSNA detected more cases of non-SN metastases than histology (OSNA 66/119, 55.5% vs histology 13/64, 20.3% P<0.001), particularly micrometastases (36/119, 30.3% vs 1/64, 1.6% P<0.001). Total upstaging rates were similar in both cohorts (20/119, 16.8% vs 9/64, 14.1%, P=0.79). Conclusion: OSNA detects a far greater proportion of non-SN micrometastases than routine histological examination. However, upstaging rates after axillary dissection were not significantly different between both cohorts. Follow-up of the OSNA cohort is required to determine its clinical relevance.

Osako, T; Iwase, T; Kimura, K; Yamashita, K; Horii, R; Akiyama, F

2011-01-01

130

Improved CYP3A4 Molecular Models Accurately Predict Phe215 Requirement for Raloxifene Dehydrogenation Selectivity  

PubMed Central

The use of molecular modeling in conjunction with site-directed mutagenesis has extensively been used to study substrate orientation within cytochrome P450 active sites, and to identify potential residues involved in positioning and catalytic mechanisms of these substrates. However, because docking studies utilize static models to simulate dynamic P450 enzymes, the effectiveness of these studies are highly dependent on accurate enzyme models. This study employed a cytochrome P450 3A4 (CYP3A4) crystal structure (PDB code:1W0E) to predict the sites of metabolism of the known CYP3A4 substrate raloxifene. In addition, partial charges were incorporated into the P450 heme moiety to investigate the effect of the modified CYP3A4 model on metabolite prediction with the ligand-docking program Autodock. Dehydrogenation of raloxifene to an electrophilic di-quinone methide intermediate has been linked to the potent inactivation of CYP3A4. Active site residues involved in the positioning and/or catalysis of raloxifene supporting dehydrogenation were identified with the two models, and site-directed mutagenesis studies were conducted to validate the models. The addition of partial charges to the heme moiety increased accuracy of the docking studies, increasing the number of conformations predicting dehydrogenation, and facilitating the identification of substrate/active site residue interactions. Based on the improved model, the Phe215 residue was hypothesized to play an important role in orienting raloxifene for dehydrogenation through a combination of electrostatic and steric interactions. Substitution of this residue with glycine or glutamine significantly decreased dehydrogenation rates without concurrent changes in the rates of raloxifene oxygenation. Thus, the improved structural model predicted novel enzyme/substrate interactions that control the selective dehydrogenation of raloxifene to its protein-binding intermediate.

Moore, Chad D.; Shahrokh, Kiumars; Sontum, Stephen F.; Cheatham, Thomas E.; Yost, Garold S.

2010-01-01

131

Experimental studies on optimal molecular weight distribution control in a batch-free radical polymerization process  

Microsoft Academic Search

An experimental study on the control of polymer weight chain length distribution is presented for batch-free radical solution polymerization of methyl methacrylate. The weight chain length distribution is calculated using the method of finite molecular weight moments in which the weight fraction of polymers over a number of finite chain length intervals covering the theoretically infinite chain length domain is

Timothy J. Crowley; Kyu Yong Choi

1998-01-01

132

A regularization-free method for the calculation of molecular weight distributions from dynamic moduli data  

Microsoft Academic Search

There are several models for the determination of molecular weight distributions (MWDs) of linear, entangled, polymer melts via rheometry. Typically, however, models require a priori knowledge of the critical molecular weight, the plateau modulus, and parameters relating relaxation time and molecular weight (e.g., k and a in t=kMa). Also, in an effort to obtain the most general MWD or to

Job D. Guzmán; Jay D. Schieber; Richard Pollard

2005-01-01

133

Exposure assessment of high molecular weight sensitisers: contribution to occupational epidemiology and disease prevention  

Microsoft Academic Search

An important group of sensitising agents are so called high molecular weight sensitisers--proteins or glycoproteins with molecular weights in the 5-70 kDa range that can provoke a specific IgE response in workers exposed to these agents. Exposure to high molecular weight sensitisers could only be evaluated indirectly in the recent past. Few measurement techniques existed that made it possible to

D. Heederik; Doekes de G; M. J. Nieuwenhuijsen

1999-01-01

134

Compressive creep characteristics of extruded ultrahigh-molecular-weight polyethylene.  

PubMed

The static compressive creep behavior of ultrahigh-molecular-weight polyethylene (UHMWPE) was studied under physiologic conditions. Specimens were machined from the center and periphery of extruded GUR 4150HP rod stock and were subjected to constant pressures of 2, 4, or 8 MPa for intervals as long as 10(4) min. The creep strain (creep divided by initial thickness) was compared to the pressure and duration of loading by using analysis of variance and linear regression analysis. The amount of creep strain increased rapidly in the early period of testing and was followed by a reduced rate of creep, which reached a steady state after approximately 4000 min. The amount and rate of creep strain increased linearly with pressure. Surprisingly, the rate of creep strain varied with the radial position in the rod stock: specimens obtained from the periphery had 8-19% larger creep strain rates than did specimens obtained from the center (p = 0.1 to p < 0.001). These results advance the characterization of creep's contribution to the in vivo penetration of the metallic component into the UHMWPE component, thereby facilitating the measurement of true in vivo wear. These data also help explain the azimuthally nonuniform deformation observed in retrieved acetabular cups. PMID:9457556

Lee, K Y; Pienkowski, D

1998-02-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

136

Immunostimulatory and antiangiogenic activities of low molecular weight hyaluronic acid.  

PubMed

The immunostimulatory activities of two low molecular weight hyaluronic acids (LMWHA-1 and LMWHA-2 with MW of 1.45×10(5) and 4.52×10(4) Da, respectively) and HA (MW, 1.05×10(6) Da) were evaluated by using in vitro cell models and in vivo animal models, and their effects on angiogenesis were measured in vivo by using the chick embryo chorioallantoic membrane (CAM) assay. The results demonstrated that LMWHA-1, LMWHA-2 and HA could promote the splenocyte proliferation, increase the activity of acid phosphatase in peritoneal macrophages and strengthen peritoneal macrophages to devour neutral red in vitro in a dose-dependent manner. Furthermore, LMWHA-1 and LMWHA-2 exhibited much stronger immunostimulatory activity than HA. For assay in vivo, LMWHA-1 and LMWHA-2 significantly increased the indices of spleen and thymus, the activity of lysozyme in serum and the swelling rate of earlap in delayed-type hypersensitivity in a dose-dependent manner. In the CAM model, the results showed that LMWHA-1, LMWHA-2 and HA suppressed angiogenesis in chicken embryos. Moreover, LMWHA-1 exhibited higher antiangiogenesis activity than LMWHA-2 and HA. All these results suggested that LMWHA might be a potential natural immunomodulator and a potential candidate compound for antiangiogenic. PMID:23727180

Ke, Chunlin; Wang, Di; Sun, Yi; Qiao, Deliang; Ye, Hong; Zeng, Xiaoxiong

2013-05-29

137

High molecular weight plant heteropolysaccharides stimulate fibroblasts but inhibit keratinocytes.  

PubMed

Konjac glucomannan (KGM) is a natural polysaccharide of ?(1-4)-D-glucomannopyranosyl backbone of D-mannose and D-glucose derived from the tuber of Amorphophallus konjac C. Koch. KGM has been reported to have a wide range of activities including wound healing. In this study we examined KGM extracts prepared from five plant species, (Amorphophallus konjac Koch, Amorphophallus oncophyllus, Amorphophallus prainii, Amorphophallus paeoniifolius and Amorphophallus elegans) for their effects on cultured human keratinocytes and fibroblasts. Extracts from A. konjac Koch, A. oncophyllus and A. prainii (but not from A. paeoniifolius or A. elegans) stimulated fibroblast proliferation both in the absence and presence of serum. However, these materials inhibited keratinocyte proliferation. The fibroblast stimulatory activity was associated with high molecular weight fractions of KGM and was lost following ethanol extraction or enzyme digestion with ?-mannanase. It was also reduced by the addition of concanavalin A but not mannose suggesting that these heteropolysaccharides are acting on lectins but not via receptors specific to mannose. The most dramatic effect of KGM was seen in its ability to support fibroblasts for 3weeks under conditions of deliberate media starvation. This effect did not extend to supporting keratinocytes under conditions of media starvation but KGM did significantly help support adipose derived stem cells under media starvation conditions. PMID:23694709

Shahbuddin, Munira; Shahbuddin, Dahlia; Bullock, Anthony J; Ibrahim, Halijah; Rimmer, Stephen; MacNeil, Sheila

2013-04-13

138

Using low molecular weight heparin in special patient populations.  

PubMed

Clinical trials evaluating low molecular weight heparin (LMWH) for the prevention and treatment of venous thromboembolism and acute coronary syndromes have led to their regulatory approval for these indications in the general population. However, certain patient populations have been excluded from these landmark clinical trials, including patients with renal insufficiency, obese patients and pregnant women. In these special populations, data on safety and efficacy is limited and typically based on pharmacokinetic studies often performed in healthy subjects, or small cohort studies which are generally not powered to evaluate clinical outcomes such as bleeding or recurrent thrombosis. Because LMWH is mainly cleared renally, patients with severe renal insufficiency are at risk of LMWH accumulation and increased bleeding risks. In obese patients, there is concern regarding possible overdosing of therapeutic dose LMWH, since LMWH does not distribute in fat tissue. There are also concerns about possible underdosing of prophylactic dose LMWH in obese individuals using the standard fixed doses, particularly in the extremely obese individuals undergoing bariatric surgery. Last, pregnancy poses challenges with regards to the safety of LMWH during pregnancy and use of LMWH around delivery. This review summarizes the existing data in these special populations and proposes general recommendations for practice. PMID:19902146

Lim, Wendy

2010-02-01

139

Survey of hospital policies regarding low-molecular-weight heparins.  

PubMed

Hospital policies regarding the use of low-molecular-weight heparins (LMWHs) were studied. A questionnaire addressing the formulary status of LMWH products, the use of prescribing guidelines, programs for therapeutic interchange, and policies to promote alternatives to LMWHs when appropriate was prepared. The questionnaire was mailed in January 2001 to pharmacy directors at 70 hospitals located in 19 states. All the hospitals were members of a national group purchasing organization. Forty-nine usable responses were received, for a response rate of 70%. Enoxaparin and dalteparin were the LMWH products most likely to be on the respondents' formularies (98% and 29% of hospitals, respectively). About 29% of the hospitals reported having guidelines on the use of LMWHs. Among hospitals that did not, most indicated that they were considering or would like to implement such guidelines. The most commonly cited barrier to the development and implementation of guidelines was lack of pharmacy personnel. Ten percent of the respondents reported having therapeutic-interchange programs for LMWHs. Cited barriers to therapeutic interchange programs included lack of therapeutic equivalence among products and lack of comparable labeled indications. Policies to promote alternatives to LMWHs were reported by 18% of the respondents. A multihospital survey showed that many hospitals wanted but relatively few had prescribing guidelines for LMWHs. PMID:11908246

Schumock, Glen T; Nutescu, Edith A; Walton, Surrey M; Arondekar, Bhakti V; Lewis, Richard K

2002-03-15

140

Fatigue crack propagation behavior of ultrahigh molecular weight polyethylene.  

PubMed

The relative fatigue crack propagation resistance of plain and carbon fiber-reinforced ultrahigh molecular weight polyethylene (UHMWPE) was determined from cyclic loading tests performed on compact tension specimens machined from the tibial components of total knee prostheses. Both materials were characterized by dynamic mechanical spectroscopy, X-ray diffraction, and differential scanning calorimetry. The cyclic tests used loading in laboratory air at 5 Hz using a sinusoidal wave form. Dynamic mechanical spectroscopy showed that the reinforced UHMWPE had a higher elastic storage modulus than the plain UHMWPE, whereas X-ray diffraction and differential scanning calorimetry showed that the percent crystallinity and degree of order in the crystalline regions were similar for the two materials. Fatigue crack propagation in both materials proved to be very sensitive to small changes in the applied cyclic stress intensity range. A 10% increase in stress intensity resulted in approximately an order of magnitude increase in fatigue crack growth rate. The fatigue crack propagation resistance of the reinforced UHMWPE was found to be significantly worse than that of the plain UHMWPE. This result was attributed to poor bonding between the carbon fibers and the UHMWPE matrix and the ductile nature of the matrix itself. PMID:6491807

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

1984-01-01

141

High molecular weight kininogen binds to unstimulated platelets.  

PubMed Central

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

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

1986-01-01

142

Molecular weight fractionation of humic substances by adsorption onto minerals.  

PubMed

Molecular weight (MW) fractionation of Suwannee River fulvic acid (SRFA) and purified Aldrich humic acid (PAHA) by adsorption onto kaolinite and hematite was investigated in equilibrium and rate experiments with a size-exclusion chromatography system using ultraviolet (UV) light detection. The extent of adsorptive fractionation based on UV detection was positively correlated with the percent carbon adsorption for both humic substances (HS), although the specific fractionation pattern observed depended on the particular HS and mineral used. Higher MW fractions of SRFA, an aquatic HS, were preferentially adsorbed to both kaolinite and hematite whereas the fractionation trends for PAHA, a terrestrial peat HS, differed for the two minerals. The contrasting fractionation patterns for SRFA versus PAHA can be explained reasonably well by the different structural trends that occur in their respective MW fractions and the underlying adsorption processes. Rate studies of adsorptive fractionation revealed an initial rapid uptake of smaller HS molecules by the mineral surfaces, followed by their replacement at the surface by a much slower uptake of the larger HS molecules present in aqueous solution. PMID:16256646

Hur, Jin; Schlautman, Mark A

2003-08-15

143

Generic low-molecular-weight heparins: some practical considerations.  

PubMed

It is now widely accepted that various low-molecular-weight heparins (LMWHs) exhibit specific molecular and structural attributes that are determined by the type of manufacturing process used. For example, enoxaparin, which is prepared by benzylation followed by alkaline hydrolysis of unfractionated heparin (UFH), exhibits a double bond at the nonreducing end and the presence of a unique bicyclic structure namely 1,6 anhydromanno glucose or mannose, or both, at the reducing end. Similarly, the other LMWHs, such as dalteparin, nadroparin, tinzaparin, and parnaparin, exhibit specific structural characteristics that may contribute to their own unique biochemical and pharmacological profiles. These unique features may not exhibit any major influence on the routinely determined anti-Xa and anti-IIa activities. However, these may have an impact on the pharmacokinetics and other biological actions such as the interactions with growth factors, blood components, and vascular cells. This is the reason for the initial caution for the noninterchangeability of the anti-Xa adjusted dosing of the different LMWHs. Although the nonanticoagulant biological effects of these drugs are poorly understood at this time, they are now recognized as contributing significantly to the overall therapeutic effects of these drugs. Because some of these drugs have proved to be effective in the management of cancer-associated thrombosis and exhibit improvements in mortality outcome, these LMWHs may also produce several other effects by modulating inflammatory processes, apoptosis, and other regulatory functions related to cellular functions at different levels. Thus, the interactions of these LMWHs with antithrombin and heparin cofactor II are not the only determinants of their biological actions. Release of tissue factor pathway inhibitor (TFPI), regulation of cytokines, nitric oxide, and eicosanoids contribute to their individuality. Such properties are not only dependent on the oligosaccharide sequence and consensus sites but also depend mainly on microchemical and structural attributes in these drugs. European Pharmacopoeia (EP) and the World Health Organization (WHO) have developed guidelines to characterize these agents in terms of their molecular and biological profile. Regulatory agencies such as the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMEA) consider each of these drugs as distinct pharmacological agents. This has prompted the requirement for product-specific clinical data for the approval of their use in various clinical indications. There is a clear concern regarding the development of potential generic versions of branded products and the submissions by generic manufacturers for the regulatory approval of generic interchangeability that refers to the substitution of an apparent chemically identical and bioequivalent versions of the branded LMWHs. Currently, there are no regulatory guidelines or consensus opinions on the acceptance of generic versions of the branded products. Because the LMWHs represent not only a biological entity but also product-specific molecular and structural attributes, the acceptance of a generic version must be based on clearly defined guidelines stipulating minimal molecular and structural, biological, and clinical validation requirements. It is therefore to be stressed that each of the LMWHs is a distinct drug entity that characteristically exhibits a product-based therapeutic spectrum in different thrombotic and nonthrombotic disorders. Thus, until the establishment of valid regulatory guidelines for the generic interchangeability of the commercially available LMWHs is completed, generic substitutes are not recommended. PMID:15630677

Fareed, Jawed; Leong, Wendy L; Hoppensteadt, Debra A; Jeske, Walter P; Walenga, Jeanine; Wahi, Raisesh; Bick, Rodger L

2004-12-01

144

High Molecular Weight (HMW) Dissolved Organic Matter (DOM) in Seawater: Chemical Structure, Sources and Cycling.  

National Technical Information Service (NTIS)

The goal of this thesis was to use high resolution analytical techniques coupled with molecular level analyses to chemically characterize high molecular weight (> 1 k Da (HMW)) dissolved organic matter (DOM) isolated from seawater in an attempt to provide...

L. I. Aluwihare

1999-01-01

145

Effect of cross-linking ultrahigh molecular weight polyethylene: Surface molecular orientation and wear characteristics  

SciTech Connect

Molecular orientation at the surface layer of cross-linked ultrahigh molecular weight polyethylene (UHMWPE) has been examined. Molecular orientation has been shown to affect the wear resistance and surface mechanical properties of UHMWPE under biomechanical loading conditions. This study utilizes a nondestructive synchrotron based soft x-ray technique; near edge x-ray absorption fine structure at the carbon K-edge to examine the degree of surface molecular orientation of UHMWPE subjected to various cross-linking/sterilization techniques as a function of stress and wear. UHMWPE samples prepared under gamma irradiation, ethylene-oxide (EtO) treatment, and electron beam irradiation were worn in a wear tester systematically. Results suggest that the cross-linking resists surface orientation when the samples were under tensile and biomechanical stresses. The molecular orientation in the C-C chains in the polymer showed a monotonic decrease with an increase in gamma irradiation dosage levels. EtO sterilized samples showed more C-C chain orientation than the electron beam irradiated samples, but lower than the 30 kGy gamma irradiated samples. Ordered C-C chains in UHMWPE samples have been associated with more crystallinity or large strain plastic deformation of the polymer. Higher levels of gamma irradiation appear to induce cross-linking of C-C chains and render a polymer with more amorphous phase which resists orientation after wear and imparts wear resistance to the polymer.

Sambasivan, Sharadha; Fischer, Daniel A.; Hsu, Stephen M. [Ceramics Division, Material Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2007-07-15

146

Interaction of Antithrombin with Sulfated, Low Molecular Weight Lignins  

PubMed Central

Antithrombin, a major regulator of coagulation and angiogenesis, is known to interact with several natural sulfated polysaccharides. Previously, we prepared sulfated low molecular weight variants of natural lignins, called sulfated dehydrogenation polymers (DHPs) (Henry, B. L., Monien, B. H., Bock, P. E., and Desai, U. R. (2007) J. Biol. Chem. 282, 31891–31899), which have now been found to exhibit interesting antithrombin binding properties. Sulfated DHPs represent a library of diverse noncarbohydrate aromatic scaffolds that possess structures completely different from heparin and heparan sulfate. Fluorescence binding studies indicate that sulfated DHPs bind to antithrombin with micromolar affinity under physiological conditions. Salt dependence of binding affinity indicates that the antithrombin-sulfated DHP interaction involves a massive 80–87% non-ionic component to the free energy of binding. Competitive binding studies with heparin pentasaccharide, epicatechin sulfate, and full-length heparin indicate that sulfated DHPs bind to both the pentasaccharide-binding site and extended heparin-binding site of antithrombin. Affinity capillary electrophoresis resolves a limited number of peaks of antithrombin co-complexes suggesting preferential binding of selected DHP structures to the serpin. Computational genetic algorithm-based virtual screening study shows that only one sulfated DHP structure, out of the 11 present in a library of plausible sequences, bound in the heparin-binding site with a high calculated score supporting selectivity of recognition. Enzyme inhibition studies indicate that only one of the three sulfated DHPs studied is a potent inhibitor of free factor VIIa in the presence of antithrombin. Overall, the chemo-enzymatic origin and antithrombin binding properties of sulfated DHPs present novel opportunities for potent and selective modulation of the serpin function, especially for inhibiting the initiation phase of hemostasis.

Henry, Brian L.; Connell, Justin; Liang, Aiye; Krishnasamy, Chandravel; Desai, Umesh R.

2009-01-01

147

Antioxidant properties of some different molecular weight chitosans.  

PubMed

Chitosan, a cationic polysaccharide, is 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, relationships between molecular weight (Mr) and biological properties remain unclear. The focus of this study was on the antioxidant properties of several Mr chitosans. We measured the ability of seven Mr chitosans (CT1; 2.8 kDa, CT2; 17.0 kDa, CT3; 33.5 kDa, CT4; 62.6 kDa, CT5; 87.7 kDa, CT6; 604 kDa, CT7; 931 kDa) to protect plasma protein from oxidation by peroxyl radicals derived from 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH). A comparison of the antioxidant action of high Mr chitosans (CT6-CT7) with that of low Mr chitosans (CT1-CT5) showed that low Mr chitosans (CT1-CT5) were more effective in preventing the formation of carbonyl groups in plasma protein exposed to peroxyl radicals. AAPH substantially increases plasma protein carbonyl content via the oxidation of human serum albumin (HSA). We also measured the ability of these chitosans to protect HSA against oxidation by AAPH. Low Mr chitosans (CT1-CT5) were found to effectively prevent the formation of carbonyl groups in HSA, when exposed to peroxyl radicals. Low Mr chitosans were also good scavengers of N-centered radicals, but high Mr chitosans were much less effective. We also found a strong correlation between antioxidant activity and the Mr of chitosans in vitro. These activities were also determined by using the 'TPAC' test. These results suggest that low Mr chitosans (CT1-CT3) may be absorbed well from the gastrointestinal tract and inhibit neutrophil activation and oxidation of serum albumin that is frequently observed in patients plasma undergoing hemodialysis, resulting in a reduction in oxidative stress associated with uremia. PMID:19559405

Tomida, Hisao; Fujii, Takeshi; Furutani, Nobuko; Michihara, Akihiro; Yasufuku, Taira; Akasaki, Kenji; Maruyama, Toru; Otagiri, Masaki; Gebicki, Janusz M; Anraku, Makoto

2009-05-13

148

Thromboprophylaxis with low-molecular-weight heparin after cesarean delivery.  

PubMed

Although venous thromboembolism (VTE) is the leading cause of maternal mortality in developed countries, the usefulness of preventive low-molecular-weight heparin (LMWH) after cesarean delivery remains a matter of controversy. It was the objective of this study to evaluate the usefulness of thromboprophylaxis with LMWH after cesarean delivery. A decision model was constructed to evaluate the risks and benefits associated with a seven-day LMWH prophylaxis, compared with none. All probabilities were obtained from literature according to the highest level of evidence. We performed our analysis on two different sets of outcomes (utilities and disutilities), to calculate the quality-adjusted life expectancy at three months. Finally, we calculated the outcomes for four hypothetical cases with different risk. Prophylaxis with LMWH yielded the highest quality-adjusted life expectancy, with a net gain of 1.5-2.8 quality-adjusted days. Sensitivity analyses showed the incidence of VTE after cesarean delivery and the haemorrhagic risk related to LMWH to be critical, at threshold values of 0.15-0.22% and 0.23-0.35%, respectively. In the hypothetical cases, LMWH was safe but only marginally more effective in women with no risk factors. In case of an emergency procedure, a body-mass index >25kg/m(2), tobacco smoking, or any combination of these, reductions in VTE greatly outnumbered the increase in major haemorrhages, with a modest benefit on mortality. Our decision analysis suggests that the benefits of LMWH after cesarean delivery exceed the risks. This benefit is, however, very low in women with no risk factors. PMID:20062923

Blondon, Marc; Perrier, Arnaud; Nendaz, Mathieu; Righini, Marc; Boehlen, Francoise; Boulvain, Michel; De Moerloose, Philippe

2009-10-26

149

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

150

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

Microsoft Academic Search

Mechanical testing 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 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

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

1999-01-01

151

Influence of molecular weight on the mechanical performance of a thermoplastic glassy polyimide  

Microsoft Academic Search

Mechanical testing of an advanced thermoplastic polyimide (LaRCTM-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

L. M. Nicholson; K. S. Whitley; T. S. Gates; J. A. Hinkley

2000-01-01

152

Chitosan as Scaffold Materials: Effects of Molecular Weight and Degree of Deacetylation  

Microsoft Academic Search

In this study, we investigated in vitro the role of the degree of deacetylation and molecular weight on some biological properties of chitosan films. The influence of different degree of deacetylation and molecular weight of chitosan on the hydrophilicity, degradation, mechanical properties and biocompatibility were evaluated. The results showed that the degree of deacetylation affected the hydrophilicity and biocompatibility of

Shan-hui Hsu; Shu Wen Whu; Ching-Lin Tsai; Yuan-Hsuan Wu; Hui-Wan Chen; Kuo-Huang Hsieh

2004-01-01

153

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

154

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

155

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

156

Filtration Characteristics of MS2 Bacteriophage Using Various Molecular Weight Filters.  

National Technical Information Service (NTIS)

MS2 Bacteriophage has a reported nominal molecular weight of 2M dalton. It would be expected that this phage would not pass through filters of various sizes with low molecular weight cut off (MWCO) values of less than 1M dalton. It was discovered that MS2...

C. H. Wick P. E. McCubbin

1999-01-01

157

Are All Low Molecular Weight Heparins Equivalent in the Management of Venous Thromboembolism?  

Microsoft Academic Search

Low molecular weight heparins are replacing unfractionated heparin in a number of clinical indications because of their improved subcutaneous bioavailability and more predictable antithrombotic response. Clinical trials have demonstrated that low molecular weight heparins are at least as safe and effective as unfractionated heparin for the initial treatment of venous thromboembolism, and unfractionated heparin and warfarin for primary and secondary

Jawed Fareed; Walter Jeske; Daniel Fareed; Melaine Clark; Rakesh Wahi; Cafer Adiguzel; Debra Hoppensteadt

2008-01-01

158

Phase behavior of carbon dioxide—low-molecular weight triglycerides binary systems: measurements and thermodynamic modeling  

Microsoft Academic Search

This contribution reports new experimental data on the fluid phase behavior of binary mixtures of carbon dioxide and three saturated, low-molecular weight triglycerides: tributyrin, tricaproin and tricaprylin. The objective of this work is to analyze the effect of the triglyceride molecular weight on the phase behavior of mixtures with carbon dioxide. The experimental work covers a temperature range between 276

L. J. Florusse; T. Fornari; S. B. Bottini; C. J. Peters

2004-01-01

159

Molecular weight distribution of dissolved organic carbon in marine sediment pore waters  

Microsoft Academic Search

The molecular weight distribution of dissolved organic carbon (DOC) in pore waters from estuarine and continental margin sediments was examined using ultrafiltration techniques. The majority of this pore water DOC (?60–90%) had a molecular weight less than 3 kDa. This percentage appeared to vary systematically among the different sediments studied and showed very slight changes with depth (upper ?30 cm).

David J Burdige; Kip G Gardner

1998-01-01

160

Molecular size and weight of asphaltene and asphaltene solubility fractions from coals, crude oils and bitumen  

Microsoft Academic Search

The molecular weight of asphaltenes has been a controversy for several decades. In recent years, several techniques have converged on the size of the fused ring system; indicating that chromophores in virgin crude oil asphaltenes typically have 4–10 fused rings. Consequently, the molecular weight debate is equivalent to determining whether asphaltenes are monomeric (one fused-ring system per molecule) or whether

Sophie Badre; Cristiane Carla Goncalves; Koyo Norinaga; Gale Gustavson; Oliver. C. Mullins

2006-01-01

161

Purification and characterization of a low molecular weight zinc binding protein from human placenta  

Microsoft Academic Search

A low molecular weight, native zinc binding, cytosolic protein (LMZP) has been isolated, purified and characterized from human normal term placenta. Gel filtration of heat treated placental cytosol after sequential acetone precipitation (80% ppt) revealed a major zinc binding protein in the range of low molecular weight. This partially purified zinc binding fraction was further fractionated on DEAE-Sephadex A-25. The

S. Honey; G. I. Dhall; R. Nath

1994-01-01

162

Seven Golden Rules for heuristic filtering of molecular formulas obtained by accurate mass spectrometry  

Microsoft Academic Search

Background: Structure elucidation of unknown small molecules by mass spectrometry is a challenge despite advances in instrumentation. The first crucial step is to obtain correct elemental compositions. In order to automatically constrain the thousands of possible candidate structures, rules need to be developed to select the most likely and chemically correct molecular formulas. Results: An algorithm for filtering molecular formulas

Tobias Kind; Oliver Fiehn

2007-01-01

163

Effects of molecular weight of dextran on the adherence of Streptococcus sanguis to damaged heart valves.  

PubMed Central

Dextran-producing streptococci such as Streptococcus sanguis are the organisms most frequently associated with infective endocarditis in humans. A series of experiments was designed to study how the molecular weight of dextrans affects the adherence of an endocarditis strain of S. sanguis to canine heart valves covered with platelets and fibrin. The data indicated that this adherence was dependent on dextrans of high molecular weight, such as dextran T-2000 or glucans isolated from S. sanguis or S. mutans. The adherence properties of the strain studied were not modified by prior exposure of the bacterial cells of valve leaflets to high-molecular-weight dextrans. Preexposure of bacterial cells or valve leaflets to low-molecular-weight dextrans decreased their adherence. Low-molecular-weight dextrans interfered with adherence of dextran-positive strains to damaged heart valves.

Ramirez-Ronda, C H

1980-01-01

164

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

PubMed Central

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

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

2008-01-01

165

A modified repulsive bridge correction to accurate evaluation of solvation free energy in integral equation theory for molecular liquids  

NASA Astrophysics Data System (ADS)

Integral equation theory for molecular liquids is one of the powerful frameworks to evaluate solvation free energy (SFE). Different from molecular simulation methods, the theory computes SFE in an analytical manner. In particular, the correction method proposed by Kovalenko and Hirata [Chem. Phys. Lett. 290, 237 (1998); and J. Chem. Phys. 113, 2793 (2000)] is quite efficient in the accurate evaluation of SFE. However, the application has been limited to aqueous solution systems. In the present study, an improved method is proposed that is applicable to a wide range of solution systems. The SFE of a variety of solute molecules in chloroform and benzene solvents is evaluated. A key is the adequate treatment of excluded volume in SFE calculation. By utilizing the information of chemical bonds in the solvent molecule, the accurate computation of SFE is achieved.

Kido, Kentaro; Yokogawa, Daisuke; Sato, Hirofumi

2012-07-01

166

Low molecular weight carboxylic acids in oxidizing porphyry copper tailings.  

PubMed

The distribution of low molecular weight carboxylic acids (LMWCA) was investigated in pore water profiles from two porphyry copper tailings impoundments in Chile (Piuquenes at La Andina and Cauquenes at El Teniente mine). The objectives of this study were (1) to determine the distribution of LMWCA, which are interpreted to be the metabolic byproducts of the autotroph microbial community in this low organic carbon system, and (2) to infer the potential role of these acids in cycling of Fe and other elements in the tailings impoundments. The speciation and mobility of iron, and potential for the release of H+ via hydrolysis of the ferric iron, are key factors in the formation of acid mine drainage in sulfidic mine wastes. In the low-pH oxidation zone of the Piuquenes tailings, Fe(III) is the dominant iron species and shows high mobility. LMWCA, which occur mainly between the oxidation front down to 300 cm below the tailings surface at both locations (e.g., max concentrations of 0.12 mmol/L formate, 0.17 mmol/L acetate, and 0.01 mmol/L pyruvate at Piuquenes and 0.14 mmol/L formate, 0.14 mmol/L acetate, and 0.006 mmol/L pyruvate at Cauquenes), are observed at the same location as high Fe concentrations (up to 71.2 mmol/L Fe(II) and 16.1 mmol/L Fe(III), respectively). In this zone, secondary Fe(III) hydroxides are depleted. Our data suggest that LMWCA may influence the mobility of iron in two ways. First, complexation of Fe(III), through formation of bidentate Fe(III)-LMWCA complexes (e.g., pyruvate, oxalate), may enhance the dissolution of Fe(III) (oxy)hydroxides or may prevent precipitation of Fe(III) (oxy)hydroxides. Soluble Fe(III) chelate complexes which may be mobilized downward and convert to Fe(II) by Fe(III) reducing bacteria. Second, monodentate LMWCA (e.g., acetate and formate) can be used by iron-reducing bacteria as electron donors (e.g., Acidophilum spp.), with ferric iron as the electron acceptor. These processes may, in part, explain the low abundances of secondary Fe(III) hydroxide precipitates below the oxidation front and the high concentrations of Fe(II) observed in the pore waters of some low-sulfide systems. The reduction of Fe(III) and the subsequent increase of iron mobility and potential acidity transfer (Fe(II) oxidation can result in the release of H+ in an oxic environment) should be taken in account in mine waste management strategies. PMID:15884343

Dold, Bernhard; Blowes, David W; Dickhout, Ralph; Spangenberg, Jorge E; Pfeifer, Hans-Rudolf

2005-04-15

167

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

PubMed

A thermophilic bacterium capable of low-molecular-weight polyethylene (LMWPE) degradation was isolated from a compost sample, and was identified as Chelatococcus sp. E1, through sequencing of the 16S rRNA gene. LMWPE was prepared by thermal degradation of commercial PE in a strict nitrogen atmosphere. LMWPE with a weight-average-molecular-weight (Mw) in the range of 1,700-23,700 was noticeably mineralized into CO(2) by the bacterium. The biodegradability of LMWPE decreased as the Mw increased. The low molecular weight fraction of LMWPE decreased significantly as a result of the degradation process, and thereby both the number-average-molecular-weight and Mw increased after biodegradation. The polydispersity of LMWPE was either narrowed or widened, depending on the initial Mw of LMWPE, due to the preferential elimination of the low molecular weight fraction, in comparison to the high molecular weight portion. LMWPE free from an extremely low molecular weight fraction was also mineralized by the strain at a remarkable rate, and FTIR peaks assignable to C-O stretching appeared as a result of microbial action. The FTIR peaks corresponding to alkenes also became more intense, indicating that dehydrogenations occurred concomitantly with microbial induced oxidation. PMID:22661062

Jeon, Hyun Jeong; Kim, Mal Nam

2012-06-04

168

Protamine neutralisation of low molecular weight heparins and their oligosaccharide components.  

PubMed

Protamine sulphate is an effective inhibitor of heparin and is used clinically to neutralise both low molecular weight heparins (LMWH) and unfractionated heparin (UFH). However, protamine sulphate does not fully counter the anti-Xa effect of LMWH, even in excess (>40 ?g to 1 IU/ml). To investigate the molecular basis for this observation, the residual potencies in the presence and absence of plasma as well as the molecular weight profiles of commercial LMWH neutralised with increasing amounts of protamine were measured. Materials over 5000 Da are preferentially neutralised by protamine. To further investigate this molecular weight dependence, monodisperse oligosaccharides were prepared from three commercial LMWHs. The specific anti-Xa activity for the fractions increased with molecular weight, and was found to vary between the three preparations for oligosaccharides of the same molecular weight. Our results indicate that protamine sulphate neutralisation is largely dependent on molecular weight, leading to the implication that LMWHs containing a larger proportion of small oligosaccharides will not be as effectively neutralised. Protamine sulphate neutralisation of any given LMWH is also affected by the specific anticoagulant activities of its low molecular weight components, which varies between LMWH products, presumably with the method of manufacture. PMID:20922518

Schroeder, Mette; Hogwood, John; Gray, Elaine; Mulloy, Barbara; Hackett, Anne-Marie; Johansen, Kristian B

2010-10-05

169

Structural elucidation of Argonne premium coals: Molecular weights, heteroatom distributions and linkages between clusters  

SciTech Connect

The objective of this study is to create a statistically accurate picture of important structural features for a group of coals representing a broad rank range. Mass spectrometric techniques are used to study coals, coal extracts and chemically modified coals and extracts. Laser desorption mass spectrometry is used to determine molecular weight distributions. Desorption chemical ionization high resolution mass spectrometry provides detailed molecular information on compound classes of molecules is obtained using tandem mass spectrometry. These results are correlated with other direct studies on these samples such as solid NMR, XPS and X-ray absorption spectroscopy. From the complex sets of data, several general trends are emerging especially for heteroatom containing species. From a statistical point of view, heteroatoms must play important roles in the reactivity of all coals. Direct characterization of sulfur containing species in the Argonne coals has been reported from XANES analysis. Indirect methods used include: TG-FTIR and HRMS which rely on thermal desorption and pyrolysis to vaporize the samples. Both XANES and XPS data on nitrogen has been reported, but at this time, the XPS information is probably more reliable. Results from HRMS are discussed in this paper. Most other information on nitrogen is limited to analysis of liquefaction products. However, nitrogen can be important in influencing characteristics of coal liquids and as a source of NO{sub x}`s in coal combustion.

Winans, R.E.,; Kim, Y.; Hunt, J.E.; McBeth, R.L.

1995-12-31

170

A low cost, colour coded, hand held spring scale accurately categorises birth weight in low resource settings  

PubMed Central

Aims To determine the accuracy of a low cost, spring calibrated, hand held scale in classifying newborns into three weight categories (?2500?g, 2000–2499?g, <2000?g). Methods The test device was compared to a gold standard digital baby scale with precision to 2?g. In Sarlahi district, Nepal, 1890 newborns were eligible for the study. Measurements were collected for both the test device and the digital scale from 1820 (96.3%) newborns. Results The overall low birth weight (LBW) prevalence rate for the gold standard digital scale was 28.1% (511/1820). Sensitivity (93.7%) and specificity (97.6%) of the test device was high compared to LBW classifications based on digital weight measurements. Classification of infants into the <2000?g category was 5.0% and 4.7% for the gold standard and test device, respectively. Sensitivity and specificity of the test device in identifying infants <2000?g was 87.8% and 99.6%, respectively. Positive predictive values were high (>91%) for both weight categories Conclusions This low cost, simple?to?use device classified infants into weight categories with a high degree of consistency and accuracy that exceeds that of surrogate measures. This new device is useful for identifying and targeting life saving interventions for LBW, high risk infants in settings where infants are born in the home and conventional weighing scales are unavailable.

Mullany, L C; Darmstadt, G L; Coffey, P; Khatry, S K; LeClerq, S C; Tielsch, J M

2006-01-01

171

An automatic algorithm for rapid and accurate extraction of the human ventricular system from T2-weighted MR images  

NASA Astrophysics Data System (ADS)

Our previous work to segment the complete ventricular system from T1-weighted and SPGR MR images is extended here to deal with T2-weighted MR images. For each ventricle, a region of interest is determined first and its local statistics is calculated to find the intensity ranges of cerebrospinal fluid, grey matter and white matter. Then, region growing is performed in each ventricle based on the calculated statistics. During region growing, anti-leakage conditions are checked to prevent growing into extraventricular spaces. With the incorporation of domain knowledge, radiological properties and geometrical constraints, the algorithm provides a means for the extraction of the ventricular system from T2-weighted MR images. Initial experimental results are presented with the extracted third and fourth ventricles.

Tian, Hui; Huang, Su; Hu, Qingmao; Aziz, Aamer; Nowinski, Wieslaw L.

2004-05-01

172

Antioxidant activity of high molecular weight chitosan and N,O-quaternized chitosans.  

PubMed

The objective of this study was to evaluate the in vitro antioxidant activity of high molecular weight chitosan based films. Three kinds of water-soluble quaternized chitosans with high molecular weight, namely N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (400-HTCC and 1240-HTCC), N-(2-hydroxyl) propyl-3-triethyl ammonium chitosan chloride (400-HTEC and 1240-HTEC), and O-(2-hydroxyl) propyl-3- trimethyl ammonium chitosan chloride (400-O-HTCC) were prepared from high molecular weight chitosans (400 and 1240 kDa). The in vitro antioxidant activity of a high molecular weight chitosan (1240-CS) and five quaternized chitosans was evaluated and compared as radical scavengers against 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH•), hydroxyl radical (•OH), and superoxide radical (•O2(-)) using established methods, and the effect of the molecular weight, the concentration, the newly generated hydroxyl group, the extra introduced positive charge of quaternary ammonium salt group, etc., on the antioxidant activity of these high molecular weight chitosans is discussed. The data obtained in vitro models exhibited good antioxidant potency and suggested the possibility that high molecular weight chitosan based films could be effectively employed as natural antioxidant materials for application in the field of food and medicine. PMID:23706102

Wan, Ajun; Xu, Qing; Sun, Yan; Li, Huili

2013-07-08

173

High Molecular Weight Petrogenic and Pyrogenic Hydrocarbons in Aquatic Environments  

NASA Astrophysics Data System (ADS)

Geochemistry is ultimately the study of sources, movement, and fate of chemicals in the geosphere at various spatial and temporal scales. Environmental organic geochemistry focuses such studies on organic compounds of toxicological and ecological concern (e.g., Schwarzenbach et al., 1993, 1998; Eganhouse, 1997). This field emphasizes not only those compounds with potential toxicological properties, but also the geological systems accessible to the biological receptors of those hazards. Hence, the examples presented in this chapter focus on hydrocarbons with known health and ecological concern in accessible shallow, primarily aquatic, environments.Modern society depends on oil for energy and a variety of other daily needs, with present mineral oil consumption throughout the 1990s exceeding 3×109 t yr-1 (NRC, 2002). In the USA, e.g., ˜40% of energy consumed and 97% of transportation fuels are derived from oil. In the process of extraction, refinement, transport, use, and waste production, a small but environmentally significant fraction of raw oil materials, processed products, and waste are released inadvertently or purposefully into the environment. Because their presence and concentration in the shallow environments are often the result of human activities, these organic materials are generally referred to as "environmental contaminants." Although such reference connotes some form of toxicological or ecological hazard, specific health or ecological effects of many organic "environmental contaminants" remain to be demonstrated. Some are, in fact, likely innocuous at the levels that they are found in many systems, and simply adds to the milieu of biogenic organic compounds that naturally cycle through the shallow environment. Indeed, virtually all compounds in crude oil and processed petroleum products have been introduced naturally to the shallow environments as oil and gas seepage for millions of years ( NRC, 2002). Even high molecular weight (HMW) polyaromatic compounds were introduced to shallow environments through forest fires and natural coking of crude oil ( Ballentine et al., 1996; O'Malley et al., 1997). The full development of natural microbial enzymatic systems that can utilize HMW hydrocarbons as carbon or energy source attests to the antiquity of hydrocarbon dispersal processes in the environment. The environmental concern is, therefore, primarily due to the rate and spatial scale by which petroleum products are released in modern times, particularly with respect to the environmental sensitivity of some ecosystems to these releases ( Schwarzenbach et al., 1993; Eganhouse, 1997; NRC, 2002).Crude oil is produced by diagenetic and thermal maturation of terrestrial and marine plant and animal materials in source rocks and petroleum reservoirs. Most of the petroleum in use today is produced by thermal and bacterial decomposition of phytoplankton material that once lived near the surface of the world's ocean, lake, and river waters (Tissot and Welte, 1984). Terrestrially derived organic matter can be regionally significant, and is the second major contributor to the worldwide oil inventory ( Tissot and Welte, 1984; Peters and Moldowan, 1993; Engel and Macko, 1993). The existing theories hold that the organic matter present in crude oil consists of unconverted original biopolymers and new compounds polymerized by reactions promoted by time and increasing temperature in deep geologic formations. The resulting oil can migrate from source to reservoir rocks where the new geochemical conditions may again lead to further transformation of the petrogenic compounds. Any subsequent changes in reservoir conditions brought about by uplift, interaction with aqueous fluids, or even direct human intervention (e.g., drilling, water washing) likewise could alter the geochemical makeup of the petrogenic compounds. Much of our understanding of environmental sources and fate of hydrocarbon compounds in shallow environments indeed borrowed from the extensive geochemical and analytical framework that was meticulo

Abrajano, T. A., Jr.; Yan, B.; O'Malley, V.

2003-12-01

174

Molecular organization of a high molecular weight multi-protease complex from rat liver.  

PubMed

A latent multifunctional protease with a molecular weight of 722,000 to 760,000 purified from rat liver cytosol has been reported. This paper reports on the structure and subunit composition of the enzyme. Electron microscopy showed that the enzyme was a ring-shaped particle of 160(+/- 7) A diameter and 110(+/- 10) A height with a small hole of 10 to 30 A diameter (1 A = 0.1 nm). Small-angle X-ray scattering analysis indicated that the enzyme had a prolate ellipsoidal structure with an ellipsoid cavity in the center. The maximum dimension of the enzyme was estimated to be 210 A from a pair-distance distribution function. The radius of gyration obtained from a Guinier plot and the Stokes radius based on the ellipsoidal model were 66 A and 76 A, respectively. On two-dimensional gel electrophoresis, the purified enzyme separated into 13 to 15 characteristic components with molecular weights of 22,000 to 33,000 and isoelectric points of 4 to 9. These multiple components were not artifacts produced by limited proteolysis during purification of the enzyme, because the cell-free translation products in a reticulocyte lysate with poly(A)-mRNA of rat liver consisted of multiple components of similar sizes, and because peptide mapping analyses with lysylendopeptidase and V8 protease demonstrated clear differences in the primary structures of these components. The 13 main components were isolated from the purified enzyme by reverse-phase high performance liquid chromatography and shown to be non-identical. A model of the enzyme is proposed on the basis of these observations and previous physicochemical studies. Interestingly, the morphology of this protease is similar to that of the 16 to 22 S ring-shaped particles found in a variety of eukaryotic organisms. The structural similarity between this multi-protease complex and various reported subcellular particles is discussed. PMID:3062184

Tanaka, K; Yoshimura, T; Ichihara, A; Ikai, A; Nishigai, M; Morimoto, Y; Sato, M; Tanaka, N; Katsube, Y; Kameyama, K

1988-10-20

175

Improved low-volatile bituminous coal representation: incorporating the molecular-weight distribution  

SciTech Connect

A large ({gt}22 000 atoms) molecular representation of Pocahontas No. 3 low-volatile bituminous coal was generated that contains 215 separate molecular entities, ranging between 78 and 3286 amu, creating a molecular-weight distribution. Data used in this construction were based on (1) the average molecular properties and the carboxylation-oxidation molecular-weight distribution, (2) aromatic 'raft' size evaluation via image analysis of lattice fringe high-resolution transmission electron microscopy images, (3) molecular-weight distribution through laser desorption mass spectrometry, and (4) physical characteristics (molecular orientation and helium density). The large-scale coal representation enabled the incorporation of molecular-weight diversity, which is an improvement to the structural modeling of coal. The large-scale model is necessary to conform to an appropriate molecular-weight distribution. A preferred orientation that is expected for a coal of this rank was imposed. The inclusion of these improvements will better enable the model to be used in application studies. 39 refs., 7 figs., 2 tabs.

Marielle R. Narkiewicz; Jonathan P. Mathews [Pennsylvania State University, University Park, PA (United States). Department of Energy and Mineral Engineering, and the Earth and Mineral Sciences Energy Institute

2008-09-15

176

Kininogen deficiency in Fitzgerald trait: role of high molecular weight kininogen in clotting and fibrinolysis.  

PubMed

Plasma from an asymptomatic person with defects in blood coagulation, release of kinin, and evolution of fibrinolytic activity upon contact with a foreign surface was deficient in kininogen. The coagulation defect was identified as "Fitzgerald trait." A preparation of high molecular weight kininogen repaired the defects in clotting, kinin release and fibrinolysis, but a preparation of low molecular weight kininogen did not. Therefore, Fitzgerald factor appears to be a high molecular weight kininogen. The site of action of the kininogen appears to be after that of activated Hageman factor and kallikrein in the generation of clot-promoting activity through activation of plasma thromboplastin antecedent (PTA). PMID:1245795

Donaldson, V H; Glueck, H I; Miller, M A; Movat, H Z; Habal, F

1976-02-01

177

Granulocyte elastase cleaves human high molecular weight kininogen and destroys its clot-promoting activity  

PubMed Central

Purified human granulocyte elastase cleaved purified human high molecular weight (HMW) kininogen into multiple low molecular weight fragments, and destroyed the clot-promoting activity of the HMW kininogen. Elastase digestion did not release kinin or destroy the bradykinin portion of the HMW kininogen molecule; kallikrein could release kinin from the elastase-induced low molecular weight digestion products of HMW kininogen. Purified alpha 1-antitrypsin prevented the destruction of the clot-promoting activity of HMW kininogen by elastase; it also delayed the clotting of normal plasma. Elastase may play a significant role in altered hemostasis as well as fibrinolysis, in areas of inflammation to which polymorphonuclear leukocytes have been attracted.

1988-01-01

178

High-molecular-weight first-generation PMR polyimides for 343 C applications  

SciTech Connect

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, D.C.; Vannucci, R.D.

1991-12-01

179

Molecular Weight Determinations of Proteins by Californium Plasma Desorption Mass Spectrometry  

NASA Astrophysics Data System (ADS)

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 were successfully analyzed by this technique. The precision of the method is good enough to permit one to follow the different steps in the conversion of porcine insulin to human insulin.

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

1984-11-01

180

Modeling the relationship between body weight and energy intake: A molecular diffusion-based approach  

PubMed Central

Background Body weight is at least partly controlled by the choices made by a human in response to external stimuli. Changes in body weight are mainly caused by energy intake. By analyzing the mechanisms involved in food intake, we considered that molecular diffusion plays an important role in body weight changes. We propose a model based on Fick's second law of diffusion to simulate the relationship between energy intake and body weight. Results This model was applied to food intake and body weight data recorded in humans; the model showed a good fit to the experimental data. This model was also effective in predicting future body weight. Conclusions In conclusion, this model based on molecular diffusion provides a new insight into the body weight mechanisms. Reviewers This article was reviewed by Dr. Cabral Balreira (nominated by Dr. Peter Olofsson), Prof. Yang Kuang and Dr. Chao Chen.

2012-01-01

181

Cyclodextrins in Nasal Delivery of Low-Molecular-Weight Heparins: In Vivo and in Vitro Studies  

Microsoft Academic Search

Purpose. To test the hypothesis that cyclodextrins reversibly enhance nasal absorption of low-molecular-weight heparins (LMWHs) and to investigate the mechanisms by which cyclodextrins enhance LMWH absorption via the nose.

Tianzhi Yang; Alamdar Hussain; Jennifer Paulson; Thomas J. Abbruscato; Fakhrul Ahsan

2004-01-01

182

Determination of Low Molecular Weight Thiols Using Monobromobimane Fluorescent Labeling and High-Performance Liquid Chromatography.  

National Technical Information Service (NTIS)

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 appli...

R. C. Fahey G. L. Newton

1988-01-01

183

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

National Technical Information Service (NTIS)

Mechanical testing of an advanced polyimide resin (LaRC(tm)-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. Elastic and inelastic properties were characterized as a function ...

J. A. Hinkley K. S. Whitley L. M. Nicholson T. S. Gates

2000-01-01

184

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

National Technical Information Service (NTIS)

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 notch...

L. M. Nicholson K. S. Whitley T. S. Gates J. A. Hinkley

1999-01-01

185

High Molecular Weight First Generation Pmr Polyimides for 343 C Applications.  

National Technical Information Service (NTIS)

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...

D. C. Malarik R. D. Vannucci

1991-01-01

186

Friction, Wear, Transfer and Wear Surface Morphology of Ultra-High-Molecular-Weight Polyethylene.  

National Technical Information Service (NTIS)

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...

R. L. Fusaro

1983-01-01

187

Ultra-High Molecular Weight Polyethylene Wear Particles Effects on Bioactivity.  

National Technical Information Service (NTIS)

Ultra-high molecular weight polyethylene (UHMWPE) wear particles have been recognized as one of the major causes of aseptic loosening in total joint replacements. Macrophage phagocytosis of wear particles induces human biological/physiological responses w...

H. W. Fang J. V. Sengers S. M. Hsu

2003-01-01

188

Relationship Between Morphology and Mechanical Properties of Ultra High Molecular Weight Polyethylene.  

National Technical Information Service (NTIS)

Aspects of the morphology of the constituent particles of the raw ultra high molecular weight polyethylene (UHMWPE) used in this study have been examined using scanning electron microscopy. In addition differential scanning calorimetry has been used to de...

G. B. McKenna F. A. Khoury J. M. Crissman

1981-01-01

189

Crosslinked, Flexible, Low-Molecular-Weight Polyacrylamide Gels for Mobility Control: Topical Report.  

National Technical Information Service (NTIS)

This project is a continuation of a research program initiated in FY88 to develop shear-resistant flexible gels based on crosslinking a low-molecular-weight polyacrylamide for mobility control. Polyacrylamide was crosslinked with aluminum citrate and chro...

H. W. Gao

1989-01-01

190

Glandulin, a Low-Molecular Weight Antimicrobial Factor Derived from Nasal Secretions.  

National Technical Information Service (NTIS)

Nasal mucosal secretions contain a variety of high molecular weight proteins from several sources which possess antimicrobial activity. Lactoferrin, a 78,000 MW glandular protein, is bacteriostatic to a wide range of Gram-negative microorganisms. The acti...

M. A. Kaliner P. B. Silver

1991-01-01

191

Synthesis of Primary-Alcohol-Terminated Polyepichlorohydrin with Molecular Weight of 4000 to 12000.  

National Technical Information Service (NTIS)

Previous studies of cationic polymerization of epichlorohydrin (ECH) indicate that the commonly used initiator systems, Lewis acid alcohol or tertiary oxonium salt alcohol complexes give polyepichlorohydrin (PECH) whose average molecular weight is less th...

C. S. Kim R. Fish P. Curb C. Youn L. Kho

1989-01-01

192

Oxidation of Large Molecular Weight Hydrocarbons in a Pressurized Flow Reactor.  

National Technical Information Service (NTIS)

The preignition behavior of several large molecular weight hydrocarbons, neat and binary mixtures, has been examined in a pressurized flow reactor in the low and intermediate temperature regime (600 800 K) at elevated pressures (8 atm). The hydrocarbons e...

D. B. Lenhert D. L. Miller N. P. Cernansky

2005-01-01

193

Antitumor activity of degraded products of lentinan: its correlation with molecular weight.  

PubMed

Lentinan, an antitumor polysaccharide from Lentinus edodes, was degraded to seven fractions by treatment with formic acid. The low molecular-weight fractions (I and II) showed no antitumor activity against sarcoma-180 solid-type tumor and the absorption maximum of Congo Red did not shift in their presence in 0.1M sodium hydroxide. The medium molecular-weight fraction III, which required the increase of doses (5 or 10 mg/kg) for inhibition of tumor growth, caused a little shift. On the other hand, the absorption maximum of Congo Red shifted largely by the presence of high molecular-weight fractions (IV approximately VII) which showed the inhibition ratio of over 95% in a dose of 1 mg/kg. Participation of molecular weight in the antitumor activity of polysaccharides which contain (1 leads to 3)-beta-D-glucan main chain was discussed. PMID:964551

Sasaki, T; Takasuka, N; Chihara, G; Maeda, Y Y

1976-04-01

194

Accurate specification of molecular structures: the case for zero-order bonds and explicit hydrogen counting.  

PubMed

Most data structures used to represent molecular entities for cheminformatics are underspecified for purposes of representing nonorganic chemical species. Two extensions are proposed: allowing bond orders of 0 and adding an atom property to control the number of inferred attached hydrogen atoms. The case for these two extensions is made by demonstrating the effective representation of a number of unconventional bonding types that cannot be effectively represented by data structures currently in common use. A set of enhancements to the industry standard MDL CTfile format is proposed, which includes a backward compatibility mechanism to maximize interpretability by software that has not been updated to make use of the extensions. PMID:22111697

Clark, Alex M

2011-12-08

195

Low molecular weight squash trypsin inhibitors from Sechium edule seeds  

Microsoft Academic Search

Nine chromatographic components containing trypsin inhibitor activity were isolated from Sechium edule seeds by acetone fractionation, gel filtration, affinity chromatography and RP-HPLC in an overall yield of 46% of activity and 0.05% of protein. The components obtained with highest yield of total activity and highest specific activity were sequenced by Edman degradation and their molecular masses determined by mass spectrometry.

Hélen J. Laure; Vítor M. Faça; Clarice lzumi; Júlio C. Padovan; Lewis J. Greene

2006-01-01

196

Molecular physiology of weight regulation in mice and humans  

Microsoft Academic Search

Evolutionary considerations relating to efficiency in reproduction, and survival in hostile environments, suggest that body energy stores are sensed and actively regulated, with stronger physiological and behavioral responses to loss than gain of stored energy. Many physiological studies support this inference, and suggest that a critical axis runs between body fat and the hypothalamus. The molecular cloning of leptin and

R L Leibel

2008-01-01

197

Synthesis and polymerization of bicyclic ketals: a practical route to high-molecular weight polyketals.  

PubMed

Polyketals are an important class of materials for drug delivery to sensitive tissues as they degrade in vivo to nonacidic species. We report the synthesis of high-molecular weight cyclic polyketals by the cationic ring-opening polymerization of bicyclic ketal monomers, which were prepared by the metal-catalyzed rearrangement of epoxy ketones. Three different cyclic polyketals with high molecular weights were synthesized using this protocol. PMID:23870014

Whiting, Bryan T; Coates, Geoffrey W

2013-07-19

198

Effects of low molecular weight organic acids on 137Cs release from contaminated soils  

Microsoft Academic Search

Radio pollutant removal is one of several priority restoration strategies for the environment. This study assessed the effect of low molecular weight organic acid on the lability and mechanisms for release of 137Cs from contaminated soils. The amount of 137Cs radioactivity released from contaminated soils reacting with 0.02M low molecular weight organic acids (LMWOAs) specifically acetic, succinic, oxalic, tartaric, and

Po Neng Chiang; Ming Kuang Wang; Pan Ming Huang; Jeng Jong Wang

2011-01-01

199

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

200

Immunochemical characterization of a human high molecular weight — melanoma associated antigen identified with monoclonal antibodies  

Microsoft Academic Search

Sodium dodecyl sulfate polyacrylamide gel analysis of a high molecular weight (HMW) human melanoma associated antigen (MAA) defined by murine monoclonal antibodies revealed a number of distinct polypeptides ranging from 80,000 up to 280,000 daltons, in addition to an extremely heterogeneous group of components distributed over a wide range in apparent molecular weight (300,000–700,000 daltons). The 280,000 dalton and the

Barry S. Wilson; Giovanna Ruberto; Soldano Ferrone

1983-01-01

201

Peptide containing microspheres from low molecular weight and hydrophilic poly( d, l-lactide-co-glycolide)  

Microsoft Academic Search

Biodegradable poly(d,l-lactide-co-glycolide) (PLGA) polymers of molecular weight lower than 30 000 Da and free terminal carboxylic acid end groups were evaluated for incorporation of a peptide. These low molecular weight hydrophilic polymers require characterization for carboxylic acid content and fraction of water soluble polymer, both of which significantly affected the structure and peptide incorporation. The polymers from different suppliers have

Rahul C. Mehta; B. C. Thanoo; Patrick P. Deluca

1996-01-01

202

Kinetics of chain collapse in dilute polymer solutions: Molecular weight and solvent dependences  

Microsoft Academic Search

The molecular weight and solvent dependences of the characteristic time of chain collapse were studied for poly(methyl methacrylate) (PMMA) of the molecular weight Mw=6.4×106 and 1.14×107 in pure acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol %). The size of PMMA chains was measured as a function of the time after the quench by static light scattering

Yasuyuki Maki; Toshiaki Dobashi; Mitsuo Nakata

2007-01-01

203

Low-molecular-weight heparin and prevention of postoperative deep vein thrombosis  

Microsoft Academic Search

The efficacy of low-molecular-weight heparin as a prophylactic agent was assessed in 150 consecutive patients over the age of 40 undergoing major abdominal surgery. Fifty of these patients received 1250 activated partial thromboplastin time (APTT) units of low-molecular-weight heparin every 12 hours: three developed isotopic deep vein thrombosis, which was confirmed by phlebography in two cases. The other 100 patients

V V Kakkar; B Djazaeri; J Fok; M Fletcher; M F Scully; J Westwick

1982-01-01

204

The role of matrix molecular weight in rubber toughened nylon 6 blends: 1. Morphology  

Microsoft Academic Search

The effects of polyamide molecular weight on morphology generation in nylon 6 blends with maleated elastomers are described. The elastomers used include styrene—butadiene—styrene block copolymers with a hydrogenated mid-block, SEBS, and versions with X % grafted maleic anhydride, SEBS-g-MA-X%, and an ethylene\\/propylene copolymer, EPR, and a maleated version EPR-g-MA. The molecular weight of the nylon 6 phase governs the melt

A. J. Oshinski; H. Keskkula; D. R. Paul

1996-01-01

205

Coating citrus (Murcott tangor) fruit with low molecular weight chitosan increases postharvest quality and shelf life  

Microsoft Academic Search

This study investigates the effects of coating with low molecular weight chitosan (LMWC, Mw=15kDa) and high molecular weight chitosan (HMWC, Mw=357kDa) on the decay of Murcott tangor and the maintenance of its quality. A 0.1% LMWC coating substantially slowed the decay of Murcott tangor stored at 15°C in relation to a control sample and reduced decay by over 20% as

Po-Jung Chien; Fuu Sheu; Hung-Ren Lin

2007-01-01

206

Effects of molecular weight of polysulfone on phase separation behavior for cyanate ester\\/polysulfone blends  

Microsoft Academic Search

The effects of molecular weight of polysulfone (PSF) on the morphology of bisphenol-A dicyanate (BADCy)\\/PSF blends were studied. Because the viscosity of the blend increased and the miscibility between BADCy and PSF decreased with the increase of PSF molecular weight, these two competing effects on the phase-separation were investigated. It was observed that the effect of viscosity was predominant: the

J. W. Hwang; K. Cho; T. H. Yoon; C. E. Park

2000-01-01

207

Release kinetics of low molecular weight solutes from mixed cellulose ethers hydrogels: a critical experimental study  

Microsoft Academic Search

Release kinetics in water of five low molecular weight model solutes (urea, cyclohexanone, acetaminophen, phenacetin, cafein) from mixed cellulose ether hydrogels have been investigated between 20°C and 60°C. Three different divinylsulfone crosslinked networks, showing acceptable mechanical resistance and variable temperature sensitivity (in terms of water swelling) have been studied. The solute molecular weight (ranging between 60 and 200×10?3kgmol?1) does not

E Favre; S Girard

2001-01-01

208

Synthesis of high molecular weight polystyrene using AGET ATRP under high pressure  

Microsoft Academic Search

High molecular weight polystyrene (PS) was synthesized by ATRP. Under atmospheric pressure (1bar), PS with Mn up to 200,000 was prepared using either ARGET or ICAR ATRP. Under high pressure (6kbar), higher molecular weight PS could be obtained due to accelerated radical propagation and diminished radical termination in polymerization of styrene. Therefore, it was possible to synthesize PS with Mn>1,000,000

Laura Mueller; Wojciech Jakubowski; Krzysztof Matyjaszewski; Joanna Pietrasik; Piotr Kwiatkowski; Wojciech Chaladaj; Janusz Jurczak

2011-01-01

209

Effects of molecular weight and stereoregularity on biodegradation of poly(vinyl alcohol) by Alcaligenes faecalis  

Microsoft Academic Search

Summary The biodegradability of poly(vinyl alcohol) (PVA) was analyzed with respect to its molecular weight and stereoregularity using the isolated PVA-assimilating microbial strain,Alcaligenes faecalis KK314. The biodegradability of PVA was influenced by its stereoregularity, and the isotactic moiety was preferentially biodegraded. However, there is no difference in the biodegradability based on the molecular weight of PVA being larger than the

Shuichi Matsumura; Yukimasa Shimura; Koutaro Terayama; Takato Kiyohara

1994-01-01

210

Isolation and function of a low molecular weight protein of mung bean embryonic axes  

Microsoft Academic Search

A low molecular weight protein from dry mung bean (Vigna radiata) embryonic axes has been purified to near homogeneity by chromatography on DEAE-cellulose and hydroxylapatite. It shows a molecular weight of about 12,000 in sodium dodecyl sulfate-polyacrylamide gels and a sedimentation coefficient of about 2 S in sucrose gradients. This protein occurs in greater amounts in dry axes than in

A. Manickam; Albert R. Carlier

1980-01-01

211

Effect of Hydrothermal Polylactic Acid Degradation on Polymer Molecular Weight and Surface Properties  

Microsoft Academic Search

In the present work, polylactic acid, PLA, samples were degraded by hydrothermal treatment, and then their molecular weights,\\u000a crystallinity, surface charges and compositions, were determined, respectively, by using viscometry, 1H NMR, Differential Scanning Calorimetry (DSC), microelectrophoresis and Infra Red spectroscopy methods. The viscometry and\\u000a 1H NMR data indicate that the molecular weight, of the polymer, decreases after the hydrothermal treatment.

E. L. Sambha’a; A. Lallam; A. Jada

2010-01-01

212

Synthesis and Characterization of Low Molecular Weight Azido Polymers as High Energetic Plasticizers  

Microsoft Academic Search

The present work describes a convenient process for the preparation of low molecular weight hydroxyl-terminated glycidyl azide polymers. The facile route involves the formation of glycidyl azide polymer in a single step. The polymerization of epichlorohydrin was carried out in dipolar aprotic solvent N,N-dimethylformamide (DMF) medium using diols as initiators in the presence of sodium azide. Various low molecular weight

Y. Murali Mohan; K. Mohana Raju

2004-01-01

213

High-molecular weight styrene-maleic acid copolymers as corrosion inhibitors for aluminium pigments  

Microsoft Academic Search

High-molecular weight styrene-maleic acid copolymers inhibit the corrosion of aluminium pigments in a mixture of water and butyl glycol at a ratio 9:1 at a pH value of 10 very effectively (protection factors up to 99%). This was proved by volumetric measurement of the corrosion product hydrogen. High-molecular weight polyacrylic acids are much less effective corrosion inhibitors for aluminium pigments.

B. Müller; T. Schmelich

1995-01-01

214

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

NASA Astrophysics Data System (ADS)

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 N.; Daggett, Joe; Naulleau, Patrick P.

2010-03-01

215

Low-Molecular-Weight Peptides in Corneal Tissue Culture Media and in Bovine Aqueous Fluid  

Microsoft Academic Search

Eight putative, low-molecular-weight peptides have been found in the media of bovine corneal tissue cocultures and in bovine aqueous fluid. By investigating amine fluid extracts from these sources by HPLC, possible amino acids, vitamins and urea were eliminated as the unknown peaks of interest. The molecular weights of these substances were equal to or less than 1,000 D. The peaks

David R. Whikehart; Brodrick Montgomery; Jacqueline D. Wells; Doris H. Sorna

1994-01-01

216

21 CFR 177.1440 - 4,4â²-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000.  

Code of Federal Regulations, 2010 CFR

...Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 177.1440 Section...Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 4,4â²-Isopropylidenediphenol-epichlo-rohydrin resins having a minimum molecular weight of 10,000 may be...

2009-04-01

217

21 CFR 177.1440 - 4,4â²-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000.  

Code of Federal Regulations, 2010 CFR

...Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 177.1440 Section...Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 4,4â²-Isopropylidenediphenol-epichlo-rohydrin resins having a minimum molecular weight of 10,000 may be...

2010-01-01

218

Coupling density functional theory to polarizable force fields for efficient and accurate Hamiltonian molecular dynamics simulations.  

PubMed

Hybrid molecular dynamics (MD) simulations, in which the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 10(3)-10(5) molecules, pose a challenge. A corresponding computational approach should guarantee energy conservation, exclude artificial distortions of the electron density at the interface between the DFT and PMM fragments, and should treat the long-range electrostatic interactions within the hybrid simulation system in a linearly scaling fashion. Here we describe a corresponding Hamiltonian DFT/(P)MM implementation, which accounts for inducible atomic dipoles of a PMM environment in a joint DFT/PMM self-consistency iteration. The long-range parts of the electrostatics are treated by hierarchically nested fast multipole expansions up to a maximum distance dictated by the minimum image convention of toroidal boundary conditions and, beyond that distance, by a reaction field approach such that the computation scales linearly with the number of PMM atoms. Short-range over-polarization artifacts are excluded by using Gaussian inducible dipoles throughout the system and Gaussian partial charges in the PMM region close to the DFT fragment. The Hamiltonian character, the stability, and efficiency of the implementation are investigated by hybrid DFT/PMM-MD simulations treating one molecule of the water dimer and of bulk water by DFT and the respective remainder by PMM. PMID:23822223

Schwörer, Magnus; Breitenfeld, Benedikt; Tröster, Philipp; Bauer, Sebastian; Lorenzen, Konstantin; Tavan, Paul; Mathias, Gerald

2013-06-28

219

Coupling density functional theory to polarizable force fields for efficient and accurate Hamiltonian molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Hybrid molecular dynamics (MD) simulations, in which the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 103-105 molecules, pose a challenge. A corresponding computational approach should guarantee energy conservation, exclude artificial distortions of the electron density at the interface between the DFT and PMM fragments, and should treat the long-range electrostatic interactions within the hybrid simulation system in a linearly scaling fashion. Here we describe a corresponding Hamiltonian DFT/(P)MM implementation, which accounts for inducible atomic dipoles of a PMM environment in a joint DFT/PMM self-consistency iteration. The long-range parts of the electrostatics are treated by hierarchically nested fast multipole expansions up to a maximum distance dictated by the minimum image convention of toroidal boundary conditions and, beyond that distance, by a reaction field approach such that the computation scales linearly with the number of PMM atoms. Short-range over-polarization artifacts are excluded by using Gaussian inducible dipoles throughout the system and Gaussian partial charges in the PMM region close to the DFT fragment. The Hamiltonian character, the stability, and efficiency of the implementation are investigated by hybrid DFT/PMM-MD simulations treating one molecule of the water dimer and of bulk water by DFT and the respective remainder by PMM.

Schwörer, Magnus; Breitenfeld, Benedikt; Tröster, Philipp; Bauer, Sebastian; Lorenzen, Konstantin; Tavan, Paul; Mathias, Gerald

2013-06-01

220

[Molecular weight analysis of physiological proteinuria in newborn infants (author's transl)].  

PubMed

The physiological protien and glycoprotein excretions in the urine samples of a larger group of newborn infants were separated according to the molecular weights by SDS polyacrylamide gel electrophoresis and compared with the protein excretions of older children. We found higher proportions of albumin, of high molecular weight (MW = molecular weight greater than or equal to 150 000 dt) and of lower molecular weight (MW less than albumin 6800 dt) proteins in the first 24-h urine samples after birth. One week after birth the low molecular weight proteins predominated because there was a substantial decrease in the excretion of albumin and of high molecular weight proteins (MW greater than or equal to 150 000 dt). We compared the patterns of protein excretion of the newborn infants with those of children aged from 2 1/2 to 15 years. These urines samples showed a typical pattern of protein excretion not correlated to the age. These findings express a transitory immaturity of the glomerular filter and of the tubular protein reabsorbing system of the newborn kidney. Apparently, the tubular protein handling normalizes later than the glomerular filtration of proteins. PMID:449252

Thanner, F; Wartha, R; Gekle, D

1979-03-15

221

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 ...

222

Compliance calibration for fatigue crack propagation testing of ultra high molecular weight polyethylene.  

PubMed

Ultra High Molecular Weight Polyethylene (UHMWPE) total joint replacement components under certain conditions are at risk of fatigue fracture. Thus, the fatigue crack inception/propagation resistance of UHMWPE is of interest. During fatigue crack propagation tests of UHMWPE, crack growth is often followed visually; however, this approach can be time consuming and requires that the specimen be accessible during testing. The objective of this study was to demonstrate the applicability of the compliance method for fatigue crack propagation tests of UHMWPE. We hypothesized that the standard calibration coefficients developed for metals may not be appropriate for UHMWPE and that different UHMWPE materials would require different compliance calibration coefficients. Three UHMWPE materials: sterilized (30 kGy); highly crosslinked and annealed (100 kGy, 130 degrees C); and highly crosslinked and remelted (100 kGy, 150 degrees C) were examined under ambient conditions. The results support the applicability of the compliance method for determination of crack length during fatigue crack propagation testing of UHMWPE. As hypothesized, the standard calibration coefficients were found to be inaccurate for UHMWPE. New UHMWPE-specific calibration coefficients were determined which predicted the crack growth behavior accurately. Also, as hypothesized, the compliance calibration coefficients for the three materials were significantly different. This is the first reported study to demonstrate the applicability of a compliance method to measure crack length in UHMWPE. PMID:16750266

Varadarajan, Ravikumar; Rimnac, Clare M

2006-06-05

223

Two-dimensional spatial coherence of excitons in semicrystalline polymeric semiconductors: Effect of molecular weight  

NASA Astrophysics Data System (ADS)

The electronic properties of macromolecular semiconductor thin films depend profoundly on their solid-state microstructure, which in turn is governed, among other things, by the processing conditions selected and the polymer's chemical nature and molecular weight. Specifically, low-molecular-weight materials form crystalline domains of cofacially ?-stacked molecules, while the usually entangled nature of higher-molecular-weight polymers leads to microstructures comprised of molecularly ordered crystallites interconnected by amorphous regions. Here, we examine the interplay between extended exciton states delocalized along the polymer backbones and across polymer chains within the ? stack, depending on the structural development with molecular weight. Such two-dimensional excitations can be considered as Frenkel excitons in the limit of weak intersite coupling. We combine optical spectroscopies, thermal probes, and theoretical modeling, focusing on neat poly(3-hexylthiophene) (P3HT)—one of the most extensively studied polymeric semiconductors—of weight-average molecular weight (Mw) of 3-450 kg/mol. In thin-film structures of high-molecular-weight materials (Mw > 50 kg/mol), a balance of intramolecular and intermolecular excitonic coupling results in high exciton coherence lengths along chains (˜4.5 thiophene units), with interchain coherence limited to ˜2 chains. In contrast, for structures of low-Mw P3HT (<50 kg/mol), the interchain exciton coherence is dominant (˜30% higher than in architectures formed by high-molecular-weight materials). In addition, the spatial coherence within the chain is significantly reduced (by nearly 25%). These observations give valuable structural information; they suggest that the macromolecules in aggregated regions of high-molecular-weight P3HT adopt a more planar conformation compared to low-molecular-weight materials. This results in the observed increase in intrachain exciton coherence. In contrast, shorter chains seem to lead to torsionally more disordered architectures. A rigorous, fundamental description of primary photoexcitations in ?-conjugated polymers is hence developed: two-dimensional excitons are defined by the chain-length dependent molecular arrangement and interconnectivity of the conjugated macromolecules, leading to interplay between intramolecular and intermolecular spatial coherence.

Paquin, Francis; Yamagata, Hajime; Hestand, Nicholas J.; Sakowicz, Maciej; Bérubé, Nicolas; Côté, Michel; Reynolds, Luke X.; Haque, Saif A.; Stingelin, Natalie; Spano, Frank C.; Silva, Carlos

2013-10-01

224

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

225

Use of Kinematic Viscosity Data for the Evaluation of the Molecular Weight of Petroleum Oils  

ERIC Educational Resources Information Center

|A new laboratory procedure for the evaluation of the mean molecular weight (mean relative molecular mass) of petroleum oils with high accuracy is described. The density and dynamic viscosity of three commercial petroleum oils are measured at different temperatures. These experimental data are used to calculate the kinematic viscosity as a…

Maroto, J. A.; Quesada-Perez, M.; Ortiz-Hernandez, A. J.

2010-01-01

226

A single MRI slice does not accurately predict visceral and subcutaneous adipose tissue changes during weight loss.  

PubMed

Earlier cross-sectional studies found that a single magnetic resonance imaging (MRI) slice predicts total visceral and subcutaneous adipose tissue (VAT and SAT) volumes well. We sought to investigate the accuracy of trunk single slice imaging in estimating changes of total VAT and SAT volume in 123 overweight and obese subjects who were enrolled in a 24-week CB-1R inverse agonist clinical trial (weight change, -7.7 ± 5.3 kg; SAT change, -5.4 ± 4.9 l, VAT change, -0.8 ± 1.0 l). VAT and SAT volumes at baseline and 24 weeks were derived from whole-body MRI images. The VAT area 5-10 cm above L(4)-L(5) (A(+5-10)) (R(2) = 0.59-0.70, P < 0.001) best predicted changes in VAT volume but the strength of these correlations was significantly lower than those at baseline (R(2) = 0.85-0.90, P < 0.001). Furthermore, the L(4)-L(5) slice poorly predicted VAT volume changes (R(2) = 0.24-0.29, P < 0.001). Studies will require 44-69% more subjects if (A(+5-10)) is used and 243-320% more subjects if the L(4)-L(5) slice is used for equivalent power of multislice total volume measurements of VAT changes. Similarly, single slice imaging predicts SAT loss less well than cross-sectional SAT (R(2) = 0.31-0.49 vs. R(2) = 0.52-0.68, P < 0.05). Results were the same when examined in men and women separately. A single MRI slice 5-10 cm above L(4)-L(5) is more powerful than the traditionally used L(4)-L(5) slice in detecting VAT changes, but in general single slice imaging poorly predicts VAT and SAT changes during weight loss. For certain study designs, multislice imaging may be more cost-effective than single slice imaging in detecting changes for VAT and SAT. PMID:22728693

Shen, Wei; Chen, Jun; Gantz, Madeleine; Velasquez, Gilbert; Punyanitya, Mark; Heymsfield, Steven B

2012-06-25

227

A Single MRI Slice Does Not Accurately Predict Visceral and Subcutaneous Adipose Tissue Changes During Weight Loss  

PubMed Central

Previous cross-sectional studies found that a single magnetic resonance imaging (MRI) slice predicts total visceral and subcutaneous adipose tissue (VAT and SAT) volumes well. We sought to investigate the accuracy of trunk single slice imaging in estimating changes of total VAT and SAT volume in 123 overweight and obese subjects who were enrolled in a 24-week CB-1R inverse agonist clinical trial (weight change, ?7.7±5.3 kg; SAT change, ?5.4±4.9 L, VAT change, ?0.8±1.0 L). VAT and SAT volumes at baseline and 24 weeks were derived from whole body MRI images. The VAT area 5–10 cm above L4–L5 (A+5–10) (R2=0.59–0.70, P<0.001) best predicted changes in VAT volume but the strength of these correlations were significantly lower than those at baseline (R2=0.85–0.90, P<0.001). Furthermore, the L4–L5 slice poorly predicted VAT volume changes (R2=0.24–0.29, P<0.001). Studies will require 44–69% more subjects if (A+5–10) is used and 243–320% more subjects if the L4–L5 slice is used for equivalent power of multi slice total volume measurements of VAT changes. Similarly, single slice imaging predicts SAT loss less well than cross-sectional SAT (R2=0.31–0.49 vs. R2=0.52–0.68, p<0.05). Results stayed the same when examined in men and women separately. A single MRI slice 5–10 cm above L4–L5 is more powerful than the traditionally used L4–L5 slice in detecting VAT changes, but in general single slice imaging poorly predicts VAT and SAT changes during weight loss. For certain study designs, multi-slice imaging may be more cost effective than single slice imaging in detecting changes for VAT and SAT.

Shen, Wei; Chen, Jun; Gantz, Madeleine; Velasquez, Gilbert; Punyanitya, Mark; Heymsfield, Steven B.

2012-01-01

228

Accurate thermodynamics for short-ranged truncations of Coulomb interactions in site-site molecular models  

NASA Astrophysics Data System (ADS)

Coulomb interactions are present in a wide variety of all-atom force fields. Spherical truncations of these interactions permit fast simulations but are problematic due to their incorrect thermodynamics. Herein we demonstrate that simple analytical corrections for the thermodynamics of uniform truncated systems are possible. In particular, results for the simple point charge/extended (SPC/E) water model treated with spherically truncated Coulomb interactions suggested by local molecular field theory [J. M. Rodgers and J. D. Weeks, Proc. Natl. Acad. Sci. U.S.A. 105, 19136 (2008)] are presented. We extend the results developed by Chandler [J. Chem. Phys. 65, 2925 (1976)] so that we may treat the thermodynamics of mixtures of flexible charged and uncharged molecules simulated with spherical truncations. We show that the energy and pressure of spherically truncated bulk SPC/E water are easily corrected using exact second-moment-like conditions on long-ranged structure. Furthermore, applying the pressure correction as an external pressure removes the density errors observed by other research groups in NPT simulations of spherically truncated bulk species.

Rodgers, Jocelyn M.; Weeks, John D.

2009-12-01

229

Affine-response model of molecular solvation of ions: Accurate predictions of asymmetric charging free energies.  

PubMed

Two mechanisms have been proposed to drive asymmetric solvent response to a solute charge: a static potential contribution similar to the liquid-vapor potential, and a steric contribution associated with a water molecule's structure and charge distribution. In this work, we use free-energy perturbation molecular-dynamics calculations in explicit water to show that these mechanisms act in complementary regimes; the large static potential (?44 kJ/mol/e) dominates asymmetric response for deeply buried charges, and the steric contribution dominates for charges near the solute-solvent interface. Therefore, both mechanisms must be included in order to fully account for asymmetric solvation in general. Our calculations suggest that the steric contribution leads to a remarkable deviation from the popular "linear response" model in which the reaction potential changes linearly as a function of charge. In fact, the potential varies in a piecewise-linear fashion, i.e., with different proportionality constants depending on the sign of the charge. This discrepancy is significant even when the charge is completely buried, and holds for solutes larger than single atoms. Together, these mechanisms suggest that implicit-solvent models can be improved using a combination of affine response (an offset due to the static potential) and piecewise-linear response (due to the steric contribution). PMID:23020318

Bardhan, Jaydeep P; Jungwirth, Pavel; Makowski, Lee

2012-09-28

230

Affine-response model of molecular solvation of ions: Accurate predictions of asymmetric charging free energies  

PubMed Central

Two mechanisms have been proposed to drive asymmetric solvent response to a solute charge: a static potential contribution similar to the liquid-vapor potential, and a steric contribution associated with a water molecule's structure and charge distribution. In this work, we use free-energy perturbation molecular-dynamics calculations in explicit water to show that these mechanisms act in complementary regimes; the large static potential (?44 kJ/mol/e) dominates asymmetric response for deeply buried charges, and the steric contribution dominates for charges near the solute-solvent interface. Therefore, both mechanisms must be included in order to fully account for asymmetric solvation in general. Our calculations suggest that the steric contribution leads to a remarkable deviation from the popular “linear response” model in which the reaction potential changes linearly as a function of charge. In fact, the potential varies in a piecewise-linear fashion, i.e., with different proportionality constants depending on the sign of the charge. This discrepancy is significant even when the charge is completely buried, and holds for solutes larger than single atoms. Together, these mechanisms suggest that implicit-solvent models can be improved using a combination of affine response (an offset due to the static potential) and piecewise-linear response (due to the steric contribution).

Bardhan, Jaydeep P.; Jungwirth, Pavel; Makowski, Lee

2012-01-01

231

Molecular weight distribution analysis by ultracentrifugation: adaptation of a new approach for mucins.  

PubMed

Mucins are the key macromolecular component of mucus, nature's natural lubricant, and one of the most important physical properties is their molecular weight distribution. A new approach for polydisperse polymers was recently published based on sedimentation velocity in the analytical ultracentrifuge and converts a distribution of sedimentation coefficient g(s) vs. s plot into a distribution of molecular weight utilising the power-law or scaling relationship between the sedimentation coefficient and molecular weight, s=?sMw(b) where s is the sedimentation coefficient, Mw is the weight average molecular weight and ?s and b are characteristic coefficients related to conformation. We investigate the possibility of using a large database of previously published values of s an M to define ?s and b for both aqueous solution and aqueous solution supplemented by 6M guanidine hydrochloride (a solvent which helps to minimise sample degradation). These values are then applied to a study of the molecular weight distributions of preparations of human gastric mucin in the different solvents and at different stages of purification. PMID:23465917

Gillis, Richard B; Adams, Gary G; Wolf, Bettina; Berry, Monica; Besong, Tabot M D; Corfield, Anthony; Kök, Samil M; Sidebottom, Ray; Lafond, David; Rowe, Arthur J; Harding, Stephen E

2012-05-11

232

Rheological and microstructural investigation of oat ?-glucan isolates varying in molecular weight.  

PubMed

The rheological properties and microstructure of aqueous oat ?-glucan solutions varying in molecular weight were investigated. The structural features and molecular weights (MW) were characterized by (13)C NMR spectroscopy and high performance size-exclusion chromatography (HPSEC), respectively. The microstructure of the ?-glucans dispersions was also examined by atomic force microscopy (AFM). The samples with ?-glucan content between 78 and 86% on a dry weight basis had MW, intrinsic viscosity ([?]) and critical concentration (c*) in the range of 142-2800×10(3)g/mol, 1.7-7.2dl/g and 0.25-1.10g/dl, respectively. The flow and viscoelastic behaviour was highly dependent on MW and on the concentration of the ?-glucans dispersions. Pseudoplastic behaviour was exhibited at high concentrations and Newtonian behaviour was evident at low concentrations. At the same concentration, the viscosity was higher for higher MW samples. The Cox-Merz rule was applicable for the lower molecular weight samples at higher concentrations whereas the high molecular weight sample deviated at concentrations greater than 1.0%, w/v. The mechanical spectra with variation of both MW and concentration were typical of entangled biopolymer solutions. AFM images revealed the formation of clusters or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size increased with the molecular weight of the samples investigated and has been linked to the rheological behaviour of the samples. PMID:21640753

Agbenorhevi, Jacob K; Kontogiorgos, Vassilis; Kirby, Andrew R; Morris, Victor J; Tosh, Susan M

2011-05-26

233

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

234

Low-molecular-weight polyethylenimine as a non-viral vector for DNA delivery: comparison of physicochemical properties, transfection efficiency and in vivo distribution with high-molecular-weight polyethylenimine  

Microsoft Academic Search

Low-molecular-weight polyethylenimine (LMW-PEI) was synthesized by the acid-catalyzed, ring-opening polymerization of aziridine and compared with commercially available high-molecular-weight PEI (HMW-PEI) of 25 kDa. Molecular weights were determined by size-exclusion chromatography in combination with multi-angle laser light scattering. The weight average molecular weight (Mw) of synthesized LMW-PEI was determined as 5.4±0.5 kDa, whereas commercial HMW-PEI showed a Mw of 48±2 kDa.

Klaus Kunath; Anke von Harpe; Dagmar Fischer; Holger Petersen; Ulrich Bickel; Karlheinz Voigt; Thomas Kissel

2003-01-01

235

Low molecular weight squash trypsin inhibitors from Sechium edule seeds.  

PubMed

Nine chromatographic components containing trypsin inhibitor activity were isolated from Sechium edule seeds by acetone fractionation, gel filtration, affinity chromatography and RP-HPLC in an overall yield of 46% of activity and 0.05% of protein. The components obtained with highest yield of total activity and highest specific activity were sequenced by Edman degradation and their molecular masses determined by mass spectrometry. The inhibitors contained 31, 32 and 27 residues per molecule and their sequences were: SETI-IIa, EDRKCPKILMRCKRDSDCLAKCTCQESGYCG; SETI-IIb, EEDRKCPKILMRCKRDSDCLAKCTCQESGYCG and SETI-V, CPRILMKCKLDTDCFPTCTCRPSGFCG. SETI-IIa and SETI-IIb, which differed by an amino-terminal E in the IIb form, were not separable under the conditions employed. The sequences are consistent with consensus sequences obtained from 37 other inhibitors: CPriI1meCk_DSDCla_C_C_G_CG, where capital letters are invariant amino acid residues and lower case letters are the most preserved in this position. SETI-II and SETI-V form complexes with trypsin with a 1:1 stoichiometry and have dissociation constants of 5.4x10(-11)M and 1.1x10(-9)M, respectively. PMID:16406091

Laure, Hélen J; Faça, Vítor M; Izumi, Clarice; Padovan, Júlio C; Greene, Lewis J

2006-01-09

236

Development of a bond-valence based interatomic potential for BiFeO3 for accurate molecular dynamics simulations.  

PubMed

We present an atomistic potential for BiFeO(3) based on the principles of bond-valence (BV) and bond-valence vector (BVV) conservation. The validity of this model potential is tested for both canonical ensemble (NVT) and isobaric-isothermal ensemble (NPT) molecular dynamics (MD) simulations. The model reproduces the ferroelectric-to-paraelectric phase transition in both NVT and NPT MD simulations and the temperature dependence of the local structure in BiFeO(3). The calculated domain wall energies for 71°, 109°and 180° walls agree well with density functional theory results. The success of our simple model potential for BiFeO(3) indicates that BV and BVV conservation provides a firm basis for the development of accurate atomistic potentials for complex oxides. PMID:23399759

Liu, Shi; Grinberg, Ilya; Rappe, Andrew M

2013-02-12

237

Modified tight-binding model for fast and accurate estimation of thermochemistry and molecular structure. Parameters and results for hydrocarbons  

NASA Astrophysics Data System (ADS)

A modified tight-binding method, MTB, based on the orthogonal scheme, is described. The parameters for C and H atoms are reported. The MTB values for heats of formation are surprisingly close to the experimental data. The mean absolute error (MAE) of 2.4 kcal/mol is considerably smaller than that of B3LYP and MAEs of the standard semiempirical calculations. The MTB method provides accurate molecular geometries; MAEs of the calculated bond lengths and bond angles are 0.011 Å and 1.6°, respectively. Also, activation barriers and vibrational frequencies are well reproduced. The scheme is very promising for atomic simulations of carbon nanostructures and hydrocarbon systems.

Voityuk, Alexander A.

2006-12-01

238

Determination of the molecular weight distribution of the PEGylated bovine hemoglobin (PEG-bHb).  

PubMed

The method to determine the average molecular weight and distribution of molecular weight of the PEGylated hemoglobin (PEG-bHb) and their molecular weight of polypeptides in PEG-bHb with UV absorbance (UV), light scattering (LS) and refractive index (RI) detectors is described in this paper. The results indicate that when molar ratio of PEG to hemoglobin is 7:1, the average molecular weight of PEG-bHb (M(CP) is 95 kDa, the average molecular weigh of protein moiety in PEG-bHb (M(P)) is 68 kDa, and their distribution is from 48-157 kDa and 44-121 kDa, respectively; when the molar ratio is 10:1, the M(CP) is 106 kDa, the M(P) is 70kDa, and their distribution is from 56-216kDa, 49-135kDa, respectively; when the molar ratio is 13:1, the M(CP) is 73kDa, and their distribution is from 81-272 kDa and 41-144 kDa, respectively. It has been proved that this method is a simple and reliable way for the determination of average molecular weight and distribution of molecular weight of PEGlyted hemoglobin. This experiment also suggests that there exists not only aggregation in the frontal of elution peak of PEG-bHb, but dissociation of tetramer of hemoglobin into dimmer in the tail of elution peak, and the degree of aggregation is depended on the molar ratio of PEG to hemoglobin due to the present of diol PEG and the dissociation is dependant on the concentration of hemoglobin. PMID:15768562

Li, Xianzhong; Zhang, Xiaowei; Liu, Qian

2005-01-01

239

Supramolecular star polymers. Increased molecular weight with decreased polydispersity through self-assembly.  

PubMed

A ditopic structure containing two heterocyclic DeAP units and programmed to self-assemble is used as an initiation unit for the synthesis of polylactide and polystyrene. The resultant polymers self-assemble into higher molecular weight structures with a lower molecular weight distribution. The largest discrete nanoscale polymeric assembly is proposed to be a hexameric star with a molecular weight of ca. 92.7 kDa. All polymeric assemblies generally exhibit PDI values of 1.3 to 1.5, which are lower than the PDI value of the corresponding polymeric arms. A hexameric assembly is stabilized by 30 hydrogen bonds, including six AADD.DDAA contacts. The hexameric star is formed under conditions that are at least partially controlled by kinetics. PMID:17983229

Todd, Eric M; Zimmerman, Steven C

2007-11-06

240

Investigation of the molecular weight increase of commercial lignosulfonates by laccase catalysis.  

PubMed

Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed. PMID:20175586

Areskogh, Dimitri; Li, Jiebing; Gellerstedt, Göran; Henriksson, Gunnar

2010-04-12

241

Low-molecular-weight peptides in corneal tissue culture media and in bovine aqueous fluid.  

PubMed

Eight putative, low-molecular-weight peptides have been found in the media of bovine corneal tissue cocultures and in bovine aqueous fluid. By investigating amine fluid extracts from these sources by HPLC, possible amino acids, vitamins and urea were eliminated as the unknown peaks of interest. The molecular weights of these substances were equal to or less than 1,000 D. The peaks did not correspond to glutathione or bradykinin either which fall in this molecular weight range. As the cultures aged from 10 to 32 days, it was found that 5 of the 8 peptides varied in concentration. Five peptides increased in concentration to day 17 and slowly decreased afterwards. Efforts are not directed toward the identification of these peptides. PMID:8134085

Whikehart, D R; Montgomery, B; Wells, J D; Sorna, D H

1994-01-01

242

High molecular weight first generation PMR polyimides for 343 C applications  

SciTech Connect

The polymers research effort at NASA Lewis Research Center, the lead NASA Center for aeropropulsion research, has primarily focused on the development of advanced polymers for aircraft engine applications. In order to improve engine performance, studies have emphasized the use of advanced, lightweight composite materials. The effect of molecular weight on 343 C. thermo-oxidative stability (TOS), mechanical properties, and processability, of the first generation PMR polymides was investigated. Graphite fiber reinforced PMR-15, PMR-30, PMR-50, and PMR-75 composites (corresponding to formulated molecular weights of 1,500, 3,000, 5,000, and 7,500, respectively) were fabricated utilizing 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, D.C.; Vannucci, R.D. (NASA Lewis Research Center, Cleveland, OH (United States))

1992-07-01

243

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

244

Effect of varying polyacrylamide molecular weight on tertiary oil recovery from porous media of varying permeability  

SciTech Connect

Three different molecular weight emulsion polyacrylamides (PAA) have been tested for their ability to recover oil from a multi-permeability Berea core system. Injection of a 6.5 x 10/sup 6/, 17 x 10/sup 6/, and 36 x 10/sup 6/ molecular weight PAA resulted in oil recovery from the multiple permeability core systems of 53.4, 63.7, and 57.2 percent of the waterflood residual oil, respectively. In tests with 15 g/kg Na/sub 2/CO/sub 3/, injection of the polymer systems resulted in recoveries of 65.6, 75.3, and 68.0 percent of the waterflood residual oil, respectively. In the presence of alkali, the injection of high molecular weight PAA resulted in the reduction of fluid flow into the medium and low permeability cores with 70 to 75 percent of the tertiary oil being recovered from the high permeability core. Decreasing the PAA molecular weight to 17 x 10/sup 6/ and subsequently to 6.5 x 10/sup 6/ resulted in an increasing amount of fluid flowing through the low and medium permeability cores. While decreasing the molecular weight of the PAA resulted in increased fluid diversion, the 6.5 x 10/sup 6/ molecular weight PAA recovery efficiency was less than either of the other two polymers in the high permeability core. The data indicates selection of too large a polymer can result in less than maximum oil recovery from a heterogeneous permeability reservoir as a result of lower sweep efficiency. Selection of too small a polymer can result in less than maximum oil recovery from a heterogeneous permeability reservoir as a result of decreased oil recovery from the high permeability zones. Proper selection of polyacrylamide for a heterogeneous permeability reservoir either in the presence or in the absence of alkali will maximize oil recovery.

Ball, J.T.; Pitts, M.J.

1984-04-01

245

Molecular weight and aggregation behaviour in solution of ?- d-glucan from Poria cocos sclerotium  

Microsoft Academic Search

The weight-average molecular weights Mw and intrinsic viscosities [?] of linear ?-(1 ? 3)-d-glucan (PC3), a major polysaccharide in Poria cocos sclerotium were studied by light scattering and viscometry. The Mw values of glucan PC3 fractions in 20% cadoxen solution and in cadoxen were 20.6 × 104and 8.93 × 104, respectively. The [?] values of glucan PC3 in water-cadoxen mixtures

Lina Zhang; Qiong Ding; Pingyi Zhang; Rongping Zhu; Yihua Zhou

1997-01-01

246

Low molecular weight proteinuria in diabetic children--a marker of early diabetic nephropathy?  

PubMed

Twenty-four hour urine specimens of 67 diabetic children aged 1-17 years without any renal manifestations were examined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The excretion of high molecular weight, i.e. glomerular proteins was compared to that of low molecular weight, i.e. tubular proteins corresponding to more or less than 68,000 daltons. The glomerulo-tubular protein ratio (GTPR) obtained was significantly lower in diabetic patients compared with 30 healthy children of the same age and showed a linear decrease with longer duration of diabetes. PMID:3991556

Wartha, R; Nebinger, D; Gekle, D

1985-01-01

247

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

248

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.degree. C. at a pH range of from about 2 to about 7, has an inactivation temperature of about 80.degree. C. at a pH range of from about 2 to about 7 and has a molecular weight of about 50.5-54.5 kD as determineded by SDS-PAGE.

Himmel, Michael E. (Littleton, CO); Tucker, Melvin P. (Lakewood, CO); Adney, William S. (Golden, CO); Nieves, Rafael A. (Lakewood, CO)

1995-01-01

249

Photocuring of stimulus responsive membranes for controlled-release of drugs having different molecular weights  

NASA Astrophysics Data System (ADS)

Intelligent drug delivery membranes were prepared by photocuring poly(acrylic acid) coatings onto poly(2-hydroxyethyl methacrylate) membranes each with model drugs of different molecular weights being incorporated. pH-responsive release behaviours of the model drugs which included sodium salicylate, nicotinamide, nicotinic acid, methylene blue, brilliant green and crystal violet were investigated. Only the membrane with methylene blue incorporated showed a clear pH-responsive release and other drug-incorporated membranes showed no intelligent behaviour. These phenomena were explained in terms of the difference in diffusivity of drugs through polymer matrices of the membranes attributable to the difference in the molecular weights of drugs.

Ng, Loo-Teck; Nakayama, Hiroshi; Kaetsu, Isao; Uchida, Kumao

2005-06-01

250

Dyed-polyvinyl alcohol films: molecular weight and hydrolysis degree influence on optical recording  

NASA Astrophysics Data System (ADS)

An analysis of different polyvinyl alcohol films dyed with Malachite Green is presented. Absorbance and diffraction efficiency of holographic gratings are compared, taking as a parameter the molecular weight and hydrolysis degree of the polymer. It is observed that, using the same dye concentration, the absorption coefficient of the films increases as the molecular weight increases. The absorbance of these plates can be modified when exposed to UV light. In addition, it is found that for holographic recording there is an optimal dye-polymer system film.

Solano, Cristina; Martinez-Ponce, Geminiano; Castañeda, Carlos

2006-07-01

251

Small molecular weight protein-protein interaction antagonists: an insurmountable challenge?  

PubMed

Several years ago small molecular weight protein-protein interaction (PPI) antagonists were considered as the Mount Everest in drug discovery and generally regarded as too difficult to be targeted. However, recent industrial and academic research has produced a great number of new antagonists of diverse PPIs. This review structurally analyses small molecular weight PPI antagonists and their particular targets as well as tools to discover such compounds. Besides general discussions there will be a focus on the PPI p53/mdm2. PMID:18501203

Dömling, Alexander

2008-05-21

252

Isolation from human plasma of a plasminogen activator identical to urinary high molecular weight urokinase.  

PubMed Central

Two different plasmatic plasminogen activators (PA) can be demonstrated after sodium dodecyl sulfate polyacrylamide gel electrophoresis of plasma freshly collected from resting volunteers, followed by transfer of the gels onto plasminogen-rich fibrin-agarose plates. These two PA are also present in plasmas deficient in coagulation Factor XI, Factor XII, prekallikrein, or high molecular weight-kininogen. The slower-moving PA has an apparent 85,000 Mr and is immunologically unrelated to urokinase (UK). The faster moving PA was isolated by immunoadsorption of plasma on anti-UK IgG coupled to Sepharose 4B and appears to be identical to urinary high molecular weight-UK. Images

Tissot, J D; Schneider, P; Hauert, J; Ruegg, M; Kruithof, E K; Bachmann, F

1982-01-01

253

Rheological properties of aqueous solutions of polyethylene glycols with various molecular weights  

NASA Astrophysics Data System (ADS)

The dependences of the kinematic viscosity of dilute aqueous solutions of polyethylene glycols (PEGs) with various molecular weights in the temperature range of 293.15-323.15 K were investigated. The intrinsic viscosity, the Huggins constant, and the activation energy of a viscous flow were calculated for these solutions. Proposals regarding the structure of polymer macromolecules in solution are made. The constants of the Mark-Kuhn-Hauvink equation required to estimate the polymer molecular weights were determined for PEG-water systems at various temperatures.

Shulyak, I. V.; Grushova, E. I.; Semenchenko, A. M.

2011-03-01

254

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

2013-07-22

255

Synthesis of the Low Molecular Weight Heat Shock Proteins in Plants 1  

PubMed Central

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. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8

Mansfield, Michael A.; Key, Joe L.

1987-01-01

256

Heterogeneity of molecular weight and apolipoproteins in low density lipoproteins of healthy human males.  

PubMed

The molecular weights of five low density lipoprotein (LDL) subfractions from four normal healthy males were determined by analytic ultracentrifuge sedimentation equilibria. Protein content of each subfraction was determined by elemental CHN analysis, and weights of apoprotein peptides were calculated. Molecular weights in subfractions of increasing density were 2.92 +/- 0.26, 2.94 +/- 0.12, 2.68 +/- 0.09, 2.68 +/- 0.28 and 2.23 +/- 0.22 million Da, and protein weight percentages were 21.05, 21.04, 22.05, 23.10 and 29.10, in subfractions 1, 2, 3, 4 and 5, respectively. Total mean apoprotein weights for respective subfractions were 614 +/- 53, 621 +/- 45, 588 +/- 9, 637 +/- 83 and 645 +/- 62 KDa. In addition to a single apoprotein B-100 (apo B-100) peptide with a mean carbohydrate content of 7.1% and a molecular weight of 550 KDa per LDL particle, there may be one or more apoprotein E peptides of 34 KDa and/or apoprotein C-III of 9 KDa. In addition, subfractions 4 and 5 may contain 3-7% apolipoprotein (a). There is considerable heterogeneity among LDL subfractions as well as within the same fraction from different individuals. This heterogeneity may relate to differences in origin, metabolism and/or atherogenicity as a result of their content of apoproteins other than apo B-100. PMID:1487953

Kahlon, T S; Shore, V G; Lindgren, F T

1992-12-01

257

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

258

Laser desorption/ionization techniques in the characterization of high molecular weight oil fractions. Part 1: asphaltenes.  

PubMed

The molecular weight distribution of the asphaltene fractions of two types of crude oils from two different Italian fields (samples 1 and 2) was investigated. The analytical tools used to perform these analyses were matrix assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) mass spectrometry. After observing that the use of the matrix (as well as the addition of Ag+) did not improve the quality of the data compared to that obtained in LDI conditions, all further measurements were performed with the latter technique. Operating under usual conditions of laser power and delay time, a very low resolution was observed, showing only macroscopic differences between the two samples in the molecular weight distribution of the different components. An accurate study on the possible reasons of this undesirable behavior indicates that it can originate from space charge phenomena occurring either in the ion source region or during the flight. A valid parameterization of the delay time and the laser power allowed higher quality spectra to be obtained. Surface-enhanced laser desorption ionization (SELDI) measurements were also performed using normal phase (silica) as the sample holder surface. Under these conditions, better results are obtained, proving that the sample-surface interaction is important to achieve, by means of laser irradiation, a homogeneous set of product ions. Both asphaltene samples were fractionated in five subfractions by gel-permeation chromatography (GPC) to obtain a better separation of the molecular weight distributions; the related spectra confirmed these findings. By using different approaches, relevant and reproducible differences between the asphaltene fractions of the two oil samples were observed. PMID:16941524

Rizzi, Andrea; Cosmina, Paola; Flego, Cristina; Montanari, Luciano; Seraglia, Roberta; Traldi, Pietro

2006-09-01

259

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

260

Neutron Scattering of Solution-Grown Polymer Crystals: Molecular Dimensions Are Insensitive to Molecular Weight  

Microsoft Academic Search

Neutron scattering gives information on molecular conformations in solid solutions of polymers of one isotope in another. Results on crystals of polyethylene grown from solution show a molecular dimension (in the form of a radius of gyration) that is almost invariant with the length of the chain. It is proposed that certain lengths of folded chains fold back onto themselves

D. M. Sadler; A. Keller

1979-01-01

261

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

Microsoft Academic Search

Here, we report an ultra-rapid method for the transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In this procedure, the electro-transfer was performed with heated (70–75 °C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight proteins (a purified protein, molecular weight

Biji T Kurien; R. Hal Scofield

2002-01-01

262

Development of molecular simulation methods to accurately represent protein-surface interactions: Method assessment for the calculation of electrostatic effects.  

PubMed

The simulation of the interactions of proteins with charged surfaces in a condensed-phase aqueous solution containing electrolytes using empirical force field based methods is predominantly governed by nonbonded interactions between the atoms of the protein, surface, and the solvent. Electrostatic effects represent the strongest type of these interactions and the type that is most difficult to accurately represent because of their long-range influence. While many different methods have been developed to represent electrostatic interactions, the particle mesh Ewald summation (PME) method is generally considered to be the most accurate one for calculating these effects. However, the PME method was designed for systems with three-dimensional (3D) periodicity, and not for interfacial systems such as the case of protein adsorption to a charged surface. Interfacial systems such as these have only two-dimensional periodicity, which may not be appropriate for treatment with PME due to the possibility that the presence of multiple charged image surfaces parallel to the primary simulation cell's surface, may introduce nonphysical effects on the behavior of the charged molecules in the system. In an effort to address this issue, the authors have conducted a set of nanosecond-scale molecular dynamics simulations to calculate the equilibrium distribution of Na(+) and Cl(-) ions near a charged surface using PME and a range of radial cutoff methods for treating electrostatic interactions, where the cutoffs prevent interaction with the periodic images of the system. The resulting ion concentration profiles were compared to one another and to a continuum analytical solution of the theoretical ion distribution obtained from the Poisson-Boltzmann equation. Their results show that the PME method does not introduce the suspected nonphysical effects in the ion distributions due to the 3D periodic images of the system, thus indicating that it is appropriate for use for this type of molecular simulation. Although their interest is motivated by protein-surface interactions, the conclusions are applicable for the treatment of electrostatics in other aqueous systems with two-dimensional periodicity. PMID:20408725

Collier, Galen; Vellore, Nadeem A; Latour, Robert A; Stuart, Steven J

2009-12-01

263

Contribution of low molecular weight antioxidants to the antioxidant screen of germinated soybean seeds  

Microsoft Academic Search

Soybean seed of the Mazovia variety (Glycine max) were germinated in the dark at a constant temperature of 25°C up to 168 h (24 h × 7). Changes in content of low molecular weight antioxidants (LMWA) in the course of germination were studied. The analyzed compounds were: total phenolics, soluble proteins, tocopherols (a-T, ß-T, ? -T, d -T), reduced and

H. Zieli?ski

2003-01-01

264

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...

265

Expression of a Novel High Molecular-Weight Myosin Light Chain Kinase in Endothelium  

Microsoft Academic Search

Myosin light chain phosphorylation results in cellular contraction and is a critical component of agonist- mediated endothelial cell (EC) junctional gap formation and permeability. We have shown that this reac- tion is catalyzed by a novel high molecular-weight Ca 2 1 \\/calmodulin-dependent nonmuscle myosin light chain kinase (MLCK) isoform recently cloned in human endothelium ( Am. J. Respir. Cell Mol.

Alexander D. Verin; Virginie Lazar; Ronald J. Torry; Carlos A. Labarrere; Carolyn E. Patterson; Joe G. N. Garcia

1998-01-01

266

Lubrication and wear of ultra-high molecular weight polyethylene in total joint replacements  

Microsoft Academic Search

This paper reviews recent advances in the tribology of artificial joints. Emphasis is placed on the latest developments in understanding wear mechanisms and in wear testing of ultra-high molecular weight polyethylene (UHMWPE) materials and components. Two major advances have been made. One is the discovery and recognition of the importance of multidirectional motion in wear mechanisms and wear testing of

A Wang; A Essner; V. K Polineni; C Stark; J. H Dumbleton

1998-01-01

267

Effects of Polyacrylamide Molecular Weight, Soil Texture and Electrolyte Concentration on Drainable Porosity and Aggregate Stability  

Technology Transfer Automated Retrieval System (TEKTRAN)

The literature reports on the intricate relations between soil type and molecular weight (MW) of polyacrylamide (PAM) with respect to PAM efficacy as a soil conditioner. This relation may depend on the ability of PAM to penetrate into aggregates and thus stabilize both outer and inner aggregate surf...

268

Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer  

ERIC Educational Resources Information Center

|This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

2011-01-01

269

Method for Making High Molecular Weight, Extended pi-Conjugated Polymers.  

National Technical Information Service (NTIS)

A process for making a high molecular weight, extended Pi-conjugated polymer from a monomer comprising a heterocyclic, benzylic or phenolic ring is described. The S process comprises reacting a Lewis acid with: (a) the monomer and (b) a polyhydroxy moiety...

B. D. Martin

2001-01-01

270

Antibacterial activity of chitosans and chitosan oligomers with different molecular weights  

Microsoft Academic Search

Antibacterial activities of six chitosans and six chitosan oligomers with different molecular weights (Mws) were examined against four gram-negative (Escherichia coli, Pseudomonas fluorescens, Salmonella typhimurium, and Vibrio parahaemolyticus) and seven gram-positive bacteria (Listeria monocytogenes, Bacillus megaterium, B. cereus, Staphylococcus aureus, Lactobacillus plantarum, L. brevis, and L. bulgaricus). Chitosans showed higher antibacterial activities than chitosan oligomers and markedly inhibited growth of

Hong Kyoon No; Na Young Park; Shin Ho Lee; Samuel P Meyers

2002-01-01

271

The effect of molecular weight on the adsorption and efficacy of polysaccharide depressants  

Microsoft Academic Search

Long chain polysaccharide polymers, such as carboxymethyl cellulose (CMC) and guar gum, are commonly used in flotation to depress gangue minerals. These depressants are in widespread use in the flotation of platinum group minerals contained in the Merensky ore body where the dominant gangue minerals are talc, pyroxene and feldspar. The molecular weight and degree of substitution of these polysaccharides

B. McFadzean; P. Dicks; G. Groenmeyer; P. Harris; C. O’Connor

2011-01-01

272

Polyacrylamide Molecular Weight and Phosphogypsum Effects on Infiltration and Erosion in Semi-Arid Soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Seal formation at the surface of semi-arid soils during rainstorms reduces soil infiltration rate (IR) and causes runoff and erosion. Surface application of dry anionic polyacrylamide (PAM) with high molecular weight (MW) has been found to be effective in stabilizing soil aggregates, and decreasing ...

273

Extraction of low molecular weight polynuclear aromatic hydrocarbons from ashes of coal-operated power plants  

SciTech Connect

A new procedure based on liquid-solid chromatography for the extraction of polynuclear aromatic hydrocarbons has been implemented. This yields results analogous to those of Soxhlet extraction for low molecular weight compounds. A very important reduction in the time required for sample preparation prior to gas chromatography/mass spectrometry analysis is obtained.

Mangani, F.; Cappiello, A.; Crescentini, G.; Bruner, F.; Bonfanti, L.

1987-09-01

274

Note. Low Molecular Weight Carbohydrates in Foods Usually Consumed in Spain  

Microsoft Academic Search

Low molecular weight carbohydrates (LMWC) were determined in foods usually consumed in Spain, namely: rice, biscuits, white bread, noodles, honey, as well as the most common vegetables of the Mediterranean diet. LMWC in foods contained mono-, di- and oligosaccharides; soluble sugars ranged from 0.2% to 83.8% in rice and honey, respectively. All samples contained different amounts of sucrose, glucose and

I. Espinosa-Martos; E. Rico; P. Rupèrez

2006-01-01

275

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

Microsoft Academic Search

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°C in terms of their fracture energy, obtained by adapting the essential work of fracture (EWF) method. However, a

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

2006-01-01

276

Comparative techniques for molecular weight evaluation of poly (ethylene terephthalate) (PET)  

Microsoft Academic Search

The molecular weight evaluation of poly(ethylene terephthalate) (PET) from different sources was accomplished by using three different techniques: solution intrinsic viscosity, intrinsic viscosity from melt flow index (MFI) and size exclusion chromatography (SEC). Five PET samples were used: commercial virgin PET, designed for bottle production (BPET); virgin PET taken from the first stage of condensation polymerization, similar to fiber grade

N. B. Sanches; M. L. Dias; E. B. A. V. Pacheco

2005-01-01

277

The use of low molecular weight heparin in pediatric patients: A prospective cohort study  

Microsoft Academic Search

Objective: Low molecular weight heparins (LMWHs) offer several advantages over standard anticoagulant therapy (unfractionated heparin\\/warfarin) including predictable pharmacokinetics, minimal monitoring, and subcutaneous administration. Our objective was to determine the safety and efficacy of LMWHs in children.Methods: A prospective cohort of children treated with the LMWH enoxaparin (Rhone Poulenc Rorer) was monitored at the Hospital for Sick Children, Toronto, Canada, from

David Dix; Maureen Andrew; Velma Marzinotto; Karen Charpentier; Suzanne Bridge; Paul Monagle; Gabrielle deVeber; Michael Leaker; Anthony K. C Chan; M. Patricia Massicotte

2000-01-01

278

Self-assembly of dendritic-linear block copolymers with fixed molecular weight and block ratio.  

PubMed

Block copolymers built on a dendritic block having fixed molecular weight but different number of peripheral PEG chains were synthesised. At a fixed block ratio, these block copolymers exhibited topological transition of cylindrical micelles depending on the number of PEG chains. PMID:22249563

Jeong, Moon Gon; van Hest, Jan C M; Kim, Kyoung Taek

2012-01-17

279

Local and systemic delivery of low molecular weight heparin stimulates the reendothelialization after balloon angioplasty  

Microsoft Academic Search

Objective: Recent investigations revealed the importance of endothelial cell integrity and function in the pathogenesis of restenosis after angioplasty. Agents which stimulate reendothelialization may prevent restenosis after interventional procedures. The results of in vitro studies suggested that heparin and low molecular weight heparin administration may enhance the recovery of the endothelium. In this study the extent of endothelial denudation and

Martin Oberhoff; Simon Novak; Christian Herdeg; Andreas Baumbach; Alexander Kranzhofer; Armin Bohnet; Barbara Horch; Hartmut Hanke; Karl K. Haase; Karl R. Karsch

280

SMALL AND MIDDLE MOLECULAR WEIGHT SOLUTE CLEARANCE IN NOCTURNAL INTERMITTENT PERITONEAL DIALYSIS  

Microsoft Academic Search

? ? ? ? ? Objectives: To determine the dialysate-to-plasma (D\\/P) concentration ratios and peritoneal dialytic clearance (ClD) of substances with a wide range of molecular weights in subjects receiving a simulated nocturnal intermittent peri- toneal dialysis (NIPD) session. ? ? ? ? ? Design: Open-label single-dose study. ? ? ? ? ? Subjects: Six end-stage renal disease patients under-

Donald F. Brophy; Kevin M. Sowinski; Michael A. Kraus; Sharon M. Moe; James E. Klaunig; Bruce A. Mueller

281

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...

282

High-molecular-weight polyethylene glycol prevents lethal sepsis due to intestinal Pseudomonas aeruginosa  

Microsoft Academic Search

Background & Aims: During stress, erosion of protective intestinal mucus occurs in association with adherence to and disruption of the intestinal epithelial barrier by invading opportunistic microbial pathogens. The aims of this study were to test the ability of a high-molecular-weight polyethylene glycol compound, polyethylene glycol 15–20, to protect the intestinal epithelium against microbial invasion during stress. Methods: The ability

Licheng Wu; Olga Zaborina; Alex Zaborin; Eugene B. Chang; Mark Musch; Christopher Holbrook; James Shapiro; Jerrold R. Turner; Guohui Wu; Ka yee C. Lee; John C. Alverdy

2004-01-01

283

Size exclusion chromatography (XII). Analysis of silicon-phenyl groups in molecular weight components of polydimethylsiloxanes  

Microsoft Academic Search

Methods for the qualitative and quantitative determination of silicon-phenyl groups in molecular weight components of silicones of the Sylgard type (polydimethylsiloxanes (PDMS)) were developed. On-line size exclusion chromatography was used with differential refractometer (DR), infrared (ir) and ultraviolet (uv) detection, at 254 and 215 nm. For the qualitative analyses the mobile phase was methylene chloride, with uv detection at 254

1986-01-01

284

Relation Between Colonic Inflammation Severity and Total Low-Molecular-Weight Antioxidant Profiles in Experimental Colitis  

Microsoft Academic Search

Tissue antioxidant status is altered as a response to oxidative stress. This oxidative stress, caused by reactive oxygen species, is associated with inflammatory bowel disease (IBD). Our aim was to examine the relationship between total tissue low-molecular-weight antioxidant (LMWA) profile and inflammation severity in dinitrobenzene sulfonic acid (DNBS) experimental colitis in the rat. Rats were treated with three doses of

Sigal Blau; Ron Kohen; Paul Bass; Abraham Rubinstein

2000-01-01

285

Anterior cruciate ligament reconstruction with a braided ultrahigh molecular weight polyethylene prosthesis  

Microsoft Academic Search

The purpose of this study was to evaluate the use of a prosthetic anterior cruciate ligament (PACL) for the treatment of anterior cruciate ligament (ACL) deficient knees. Fifteen patients (mean age, 40 years; range, 27 to 51 years) underwent ACL reconstruction using a PACL made from ultrahigh molecular weight polyethylene. Eleven patients had chronic ACL insufficiency (greater than 26 weeks),

Andrew S. Rokito; Clarence L. Shields; Matthew R. Lee

1995-01-01

286

The Influence of Low Molecular Weight Polymer on the Rheological Behavior of Bentonite Suspensions  

Microsoft Academic Search

The authors showed the influence of the polyethylene oxide (PEO) of molecular weight 6 × 10 g\\/mol. on the rheological properties of the bentonite suspension (6%). The PEO presents an affinity for the bentonite particles and gradually coated the clay particles, slowing down their kinetic aggregation. The reduction of particle-particle interaction took place until steady values of the yield stress.

M. Gareche; N. Zeraibi; A. Allal; M. Amoura

2012-01-01

287

Low molecular weight of fluid in an alloy of EPDM\\/SIR [insulator applications  

Microsoft Academic Search

Ethylene propylene diene rubber (EPDM), silicone rubber (SIR) and their alloys have good performance when used as outdoor insulators. The hydrophobicity of the surface is maintained in wet and polluted conditions as a result of the presence of silicone fluid on the surface. This is sustained by the diffusion of low molecular weight (LMW) fluid from the bulk to the

K. Iida; R. Hackam

2004-01-01

288

Effectiveness of the membrane bioreactor in the biodegradation of high molecular weight compounds  

Microsoft Academic Search

This paper presents biological and physical performance data from a pilot-scale membrane bioreactor system fed with synthetic wastewater containing high molecular weight compounds. At steady state, high effluent quality was obtained and maintained for about 350days. The membrane was effective in retaining heterotrophic microorganisms and MS-2 viruses, eliminating the need for effluent disinfection. The flux through the membrane decreased rapidly

Nazim Cicek; Hans Winnen; Makram T. Suidan; Brian E. Wrenn; Vincent Urbain; Jacques Manem

1998-01-01

289

Variant high-molecular-weight glutenin subunits arising from biolistic transformation of wheat  

Technology Transfer Automated Retrieval System (TEKTRAN)

Genetic transformation via the biolistic method has been used to introduce genes encoding natural and novel high-molecular-weight glutenin subunits (HMW-GS) into wheat. The appearance of new seed proteins of sizes not predicted by the transgene coding sequences has been noted in some of these exper...

290

Development and characterization of homogeneous membranes de from high molecular weight sulfonated polyphenylene oxide  

Microsoft Academic Search

The high molecular weight polyphenylene oxide (PPO) was sulfonated to different ion exchange capacity (IEC) values using chlorosulfonic acid. The physico-chemical properties along with the gas transport properties of the membranes prepared from sulfonated PPO (SPPO) were evaluated. Sulfonation of PPO results in a linear increase of density with the IEC value while the average d-spacing in polymer remains constant.

Boguslaw Kruczek; Takeshi Matsuura

1998-01-01

291

GPU-Based Parallel Calculation Method for 1Molecular Weight Distribution of Batch Free Radical Polymerization  

Microsoft Academic Search

The rigorous model for calculating the time evolution of the molecular weight distribution (MWD) in batch free radical polymerization processes consists of a very large number of differential and algebraic equations (DAEs). A sequential variable decoupling (SVD) method has been proposed to enable the calculation in a sequential mode. With this SVD method, the calculation of MWD can be achieved

Zhiqiang Chen; Xi Chen; Zhen Yao; Zhijiang Shao

2011-01-01

292

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...

293

Effect of low molecular weight dextrins on gelatinization and retrogradation of starch  

Microsoft Academic Search

!-Amylases, usually added to bread recipes as anti-firming agents, are known to produce low molecular weight dextrins by starch hydrolysis. The influence of these compounds on the gelatinization and retrogradation of starch was studied by differential scanning calorimetry. Adding oligosaccharides to starch caused a delay in gelatinization, although its extent was not quantified. However, oligosaccharides of degrees of polymerization (DP)

Encarna Durán; Alberto León; Berta Barber; C. Benedito de Barber

2001-01-01

294

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

Microsoft Academic Search

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

James E. Rollings; Robert W. Thompson

1984-01-01

295

Ultrafiltration processes for removing humic substances: effect of molecular weight fractions and PAC treatment  

Microsoft Academic Search

The role of humic substances in general and different molecular weight fractions of humic substances in particular on the membrane performance in terms of quality (chlorination byproducts) and quantity (permeate flux) is unclear. One of the goals of the present study is to evaluate the effect of fractionated humic substances on the ultrafiltration (UF) performance. A commercial humic solution was

Cheng-Fang Lin; Yuh-Jay Huang; Oliver J Hao

1999-01-01

296

Porous balloon delivery of low molecular weight heparin in the dog coronary artery  

Microsoft Academic Search

The aim of this experimental study was to assess the safety of local delivery of low molecular weight heparin via a porous balloon in the canine coronary artery. In 16 mongrel dogs, percutaneous transluminal coronary angioplasty was performed. In addition, eight of the dogs were given 4 ml Clivarin (1500 IU) delivered locally into the coronary artery immediately after dilatation.

A. Baumbach; M. Oberhoff; K. Jochims; C. Herdeg; A. Kranzhofer; A. Safer; K. R. Karsch

297

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...

298

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 ...

299

ldentification of an Enhancer Element for the Endosperm-Specific Expression of High Molecular Weight Glutenin  

Microsoft Academic Search

Genes encoding high molecular weight (HMW) glutenin, a wheat seed storage protein, are expressed only in the developing endosperm. It was previously demonstrated that sequences essential for endosperm-specific transcrip- tion reside within 436 base pairs upstream of the initiation codon for HMW glutenin translation. We have further analyzed this region by testing the ability of a series of truncated HMW

Mark S. Thomas; Richard B. Flavel

1990-01-01

300

Influence of vegetation on low-molecular-weight carboxylic acids in soil solution—a review  

Microsoft Academic Search

Low-molecular-weight (LMW) carboxylic acids found in soils and soil solutions comprise mainly aliphatic mono-, di- and tricarboxylic acids and substituted benzoic and cinnamic acids. This review compiles current information on the content of LMW carboxylic acids in soil solutions collected by centrifugation and in lysimeters, and soil extracts in relation to type of vegetation, soil type and soil depth. Contents

Bjarne W Strobel

2001-01-01

301

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 (2.42-9.67mmol NaClO/g fiber) after modification times of 1h or longer. PMID:23987366

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

2013-06-26

302

Evaluation of models combining rheological data with the molecular weight distribution  

Microsoft Academic Search

this article is to test and to improve existing models combining rheologicaldata with the molecular weight distribution (MWD). This process oftesting and improving was separated into two distinct steps: First, the mixing behaviorof the relaxation modulus obtained from a polymer blend was investigatedand compared with the proposed mixing behavior derived from the linear and thequadratic mixing rules with a mixing

D. Maier; A. Eckstein; Cr. Friedrich; J. Honerkamp

1998-01-01

303

Biological activity of high molecular weight phenolics from olive mill wastewater.  

PubMed

Olive oil production generates large amounts of recalcitrant compounds, the olive oil mill wastewater (OMWW), which represent one of the most contaminating effluents among those produced by the agrofood industries. Nowadays, this view has changed to one that recognizes the waste as a low-cost starting material rich in bioactive compounds, particularly biophenols, that can be extracted and applied as natural antioxidants for the food and pharmaceutical industries. The data reported in this paper indicate that the OMWW extracts, besides low molecular weight antioxidant phenolics such as tyrosol and hydroxytyrosol, also contain phenolics with a molecular weight in the range of 600-5000 Da, which exhibit efficient scavenging activities against hydroxyl and peroxyl radicals. This group of phenolics includes, besides verbascoside, isoverbascoside, and an oxidized form of verbascoside, a number of higher molecular weight phenolics arising from oxidative polymerization of hydroxytyrosol and caffeic acid. Overall, these higher molecular weight phenolics prove to be, in some in vitro tests, more efficient scavengers of hydrophilic hydroxyl radicals than hydroxytyrosol, which could be used for industrial applications as natural nontoxic antioxidants. PMID:20681646

Cardinali, Angela; Cicco, Nunzia; Linsalata, Vito; Minervini, Fiorenza; Pati, Sandra; Pieralice, Maria; Tursi, Nunzia; Lattanzio, Vincenzo

2010-08-11

304

An assessment of antigenic potential of ?-lactam antibiotics, low molecular weight drugs, using guinea pig models  

Microsoft Academic Search

Allergic reactions are among the common adverse effects in humans. However, it is widely assumed that there are practically no reliable animal models for preclinical tests of low-molecular weight drugs that are available to predict such reactions. This study was designed to compare the detecting ability of test methods for antigenic potential of eight ?-lactam antibiotics with which allergic outcome

Hiroyuki Hattori; Fumie Yamaguchi; Nobuhiko Wagai; Michiyuki Kato; Mamoru Nomura

1997-01-01

305

Determination of polyethylene glycols of different molecular weight in the stratum corneum  

Microsoft Academic Search

We developed a sensitive method for determination of polyethylene glycols (PEGs) of different molecular weight (MW) in the human stratum corneum (SC) obtained by tape stripping. The analysis is based on derivatization with pentafluoropropionic anhydride (PFPA) and gas chromatography–electron capture detection (GC–ECD). The identification and quantification of PEGs was done using individual oligomers. The method showed to be suitable for

I. Jakasa; F. Calkoen; S. Kezic

2004-01-01

306

Supercritical Carbon Dioxide Sterilization of UltraHigh Molecular Weight Polyethylene  

Microsoft Academic Search

Abstract The aim of this research was to use a benign,technique for the sterilization of ultra-high molecular weight polyethylene (UHMWPE), which is broadly used in artificial joints and other medical implants. Current sterilizations methods such as gamma irradiation, ethylene oxide gas, and gas plasma can damage the polymer, thus reducing its service life, as well as create harmful byproducts. Supercritical

John Carlos Titone

307

Antioxidant and hepatoprotective activities of low molecular weight sulfated polysaccharide from Laminaria japonica  

Microsoft Academic Search

A low molecular weight sulfated polysaccharide (LMWF) was prepared from Laminaria japonica by mild acid hydrolysis. The antioxidant activity of LMWF in vitro was studied using three kinds of oxygen free radical systems. LMWF had effective scavenging abilities on superoxide radical, hydroxyl radical and hypochlorous acid directly in vitro. The hepatoprotective effect of LMWF was studied using two acute liver

Xue Zhao; Chang-Hu Xue; Zhao-Jie Li; Yue-Piao Cai; Hong-Ying Liu; Hong-Tao Qi

2004-01-01

308

Polymers with well-controlled molecular weight for DUV/VUV lithography  

NASA Astrophysics Data System (ADS)

Polymer resin is a major component of a photoresist formulation. Therefore, the performance of a photoresist strongly depends on the composition and properties of the resin in the formulation. We have developed a polymerization method, which is able to control the molecular weights along with the compositions of copolymers over a wide range of monomer for the end use in 193 nm or 157 nm photoresist applications. The method is called controlled radical polymerization (CRP). In use of this method, we successfully prepared an acrylate-type copolymer with low molecular weight distribution (PDI~1.2). Furthermore, the desired molecular weight of the polymers can be obtained easily altered by mild reaction condition change. Large-scale production has been demonstrated feasible. In the extension of the application of CRP, we also carried out the homopolymerization reaction of fluorinated norbornene-type monomers, and copolymerization of norbornene-type monomers with acrylates to be used in 157 nm photoresists. The results in this study show that this method can improve the molecular weight control on polymer synthesis. Measurement of the absorbance of some monomers and polymers on synchrotron radiation spectrometers will be presented here. Absorbances of our monomers are between 1456 and 5175 (L/mol cm). However, absorbances of our polymers show different data between SR and VASE measurement methods.

Lee, Ting-Yu; Yu, Chao-Ying; Hsu, Meei-Yu; Chang, Jui-Fa; Cheng, Bing-Ming; Lu, Hsiao-Chi; Chen, Hong-Kai; Fung, Hok-Sum

2003-06-01

309

Polymers with well-controlled molecular weight for DUV\\/VUV lithography  

Microsoft Academic Search

Polymer resin is a major component of a photoresist formulation. Therefore, the performance of a photoresist strongly depends on the composition and properties of the resin in the formulation. We have developed a polymerization method, which is able to control the molecular weights along with the compositions of copolymers over a wide range of monomer for the end use in

Ting-Yu Lee; Chao-Ying Yu; Meei-Yu Hsu; Jui-Fa Chang; Bing-Ming Cheng; Hsiao-Chi Lu; Hong-Kai Chen; Hok-Sum Fung

2003-01-01

310

Relative Genotoxicities of PAH of Molecular Weight 252 AMU in Coal Tar-Contaminated Sediment  

Microsoft Academic Search

Bioassay-directed chemical fractionation methodology was used to calculate relative mutagenic potencies of polycyclic aromatic hydrocarbons (PAH) of molecular weight 252 amu in coal tarcontaminated sediment from Sydney Harbour, Nova Scotia. A normal phase HPLC technique was used to separate organic solvent extracts into fractions containing isomeric PAH of a single benzologue class. Bioassays with Salmonella typhimurium strain YG1025 with the

C. H. Marvin; S. Mehta; D. Lin; B. E. McCarry; D. W. Bryant

2000-01-01

311

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

PubMed

Molecular weight has traditionally been the parameter most commonly used to classify uremic toxins, with a value of approximately 500 Da frequently used as a demarcation point below which the molecular weights of small nitrogenous waste products fall. This toxin group, the most extensively studied from a clinical perspective, is characterized by a high degree of water solubility and the absence of protein binding. However, uremia is mediated by the retention of a plethora of other compounds having characteristics that differ significantly from those of the previously mentioned group. As opposed to the relative homogeneity of the nitrogenous metabolite class, other uremic toxins collectively are a very heterogeneous group, not only with respect to molecular weight but also other characteristics, such as protein binding and hydrophobicity. A recently proposed classification scheme by the European Uraemic Toxin Work Group subdivides the remainder of molecules into 2 categories: protein-bound solutes and middle molecules. For the latter group, the Work Group proposes a molecular weight range (500-60,000 Da) that incorporates many toxins identified since the original middle molecule hypothesis, for which the upper molecular weight limit was approximately 2,000 Da. In fact, low-molecular-weight peptides and proteins (LMWPs) comprise nearly the entire middle molecule category in the new scheme. The purpose of this article is to provide an overview of the middle molecule class of uremic toxins, with the focus on LMWPs. A brief review of LMWP metabolism under conditions of normal (and in a few cases, abnormal) renal function will be presented. The physical characteristics of several LMWPs will also be presented, including molecular weight, conformation, and charge. Specific LMWPs to be covered will include beta 2-microglobulin, complement proteins (C3a and Factor D), leptin, and proinflammatory cytokines. The article will also include a discussion of the treatment-related factors influencing dialytic removal of middle molecules. Once these factors, which include membrane characteristics, protein-membrane interactions, and solute removal mechanisms, are discussed, an overview of the different therapeutic strategies used to enhance clearance of these compounds is provided. PMID:14681858

Clark, William R; Winchester, James F

2003-10-01

312

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

NASA Astrophysics Data System (ADS)

This study explores the geochronological utility and analytical reproducibility of separating the high-molecular-weight fraction (HMW) from eggshells of the extinct late Pleistocene ratite, Genyornis, using disposable, prepacked gel-filtration columns. The superior integrity of ratite eggshell for the retention of amino acids indicates that this biomineral is better suited for this type of investigation than previously studied molluscan shell. To evaluate the reproducibility of the gel-filtration technique, we analyzed triplicate subsamples of three eggshells of different ages. The reproducibility, based on the average intrashell variation (coefficient of variation; CV) in the extent of isoleucine epimerization (aIle/Ile) in the HMW (enriched in molecules ca. >10,000 MW) is 3%, well within the range appropriate for geochronological purposes. The average intrashell variation in the total amino acid concentration (?[aa]) of the HMW is 5%, somewhat better than for the total acid hydrolysate (TOTAL) of the same samples (7%). To evaluate the relation between molecular weight and the rate of isoleucine epimerization, three molecular-weight fractions were separated using gel filtration, plus the naturally hydrolyzed free fraction (FREE), for each of four fossil eggshells. AIle/Ile increases with decreasing molecular weight in all shells, with a ca. sixfold to ninefold difference in ratios between the HMW andFREE, and a ca. fivefold difference between the HMW andTOTAL. Although linear correlations between aIle/Ile measured in each molecular-weight fraction and in theTOTAL are all highly significant (r ? 0.951), the relation between the extent of epimerization in the HMW and in the TOTAL is best expressed as an exponential function (r = 0.951). This relation is consistent with the idea that, as the epimerization reaction approaches equilibrium in theTOTAL (ca. aIle/Ile > 1.1), its rate decreases beyond that of the HMW. The amino acid composition (relative percent of eight amino acids or combinations of amino acids) is more uniform in the HMW of the four samples compared to lower-molecular-weight fractions. The greater "compositional stability" of the HMW indicates that it contains a residuum of macromolecules that have not been affected by the diagenetically driven changes observed in lower-molecular-weight fractions.

Kaufman, Darrell S.; Miller, Gifford H.

1995-07-01

313

Absorption spectroscopy of the rubidium dimer in an overheated vapor: An accurate check of molecular structure and dynamics  

SciTech Connect

Experimental studies of the absorption spectrum of the Rb{sub 2} dimer are performed in the 600-1100 nm wavelength range for temperatures between 615 and 745 K. The reduced absorption coefficient is measured by spatially resolved white light absorption in overheated rubidium vapor with a radial temperature gradient, which enables simultaneous measurements at different temperatures. Semiclassical and quantum spectral simulations are obtained by taking into account all possible transitions involving the potential curves stemming from the 5 {sup 2}S+5 {sup 2}S and 5 {sup 2}S+5 {sup 2}P asymptotes. The most accurate experimental potential curves are used where available, and newly calculated potential curves and transition dipole moments otherwise. The overall consistency of the theoretical model with the experimental interpretation is obtained only if the radial dependence of both the calculated transition dipole moments and the spin-orbit coupling is taken into account. This highlights the low-resolution absorption spectroscopy as a valuable tool for checking the accuracy of molecular electronic structure calculations.

Beuc, R.; Movre, M.; Horvatic, V.; Vadla, C. [Institute of Physics, Bijenicka 46, 10000 Zagreb (Croatia); Dulieu, O.; Aymar, M. [Laboratoire Aime Cotton, CNRS, Campus d'Orsay, 91405 Orsay Cedex (France)

2007-03-15

314

How accurate are molecular mechanics predictions for fullerenes A benchmark comprison with Hartree-Fock self-consistent field results  

SciTech Connect

As research into the growing family of fullerene compounds continues to expand, theoreticians making predictions about these large carbon clusters are interested in reliable approaches to reduce the computational expense of calculations. Here we show that an empirical method, molecular mechanics (MM3), can be effectively used to optimize the geometries of fullerenes and consequently reduce the time required for more elaborate quantum mechanical calculations. Equilibrium structures and heats of formation were predicted for 22 fullerences ranging from C[sub 28] to C[sub 120] using MM3. The MM3 geometries are found to be in good agreement with those obtained by the minimum basis Hartree-Fock self-consistent field (SCF) method. However, the heats of formation obtained with MM3 and SCF are quite different. At the MM3 optimized geometry, an SCF energy point was calculated for each structure and found to be very close to the fully optimized SCF energy. This procedure yields accurate energy differences between isomers at a fraction of the computational cost. We propose other ways of using MM3 to speed ab initio calculations as well. 40 refs., 7 figs., 4 tabs.

Murry, R.L.; Colt, J.R.; Scuseria, G.E. (Rice Univ., Houston, TX (United States))

1993-05-13

315

Homology modeling and molecular dynamics simulations of the N-terminal domain of wheat high molecular weight glutenin subunit 10  

Microsoft Academic Search

High molecular weight glutenin subunits (HMW-GS) are of a particular interest because of their biome- chanical 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

ROLAND CAZALIS; THIERRY AUSSENAC; LARBI RHAZI; ANTOINE MARIN; JEAN-FRANÇOIS GIBRAT

2003-01-01

316

Low molecular weight oligomers of amyloid peptides display ?-barrel conformations: A replica exchange molecular dynamics study in explicit solvent  

NASA Astrophysics Data System (ADS)

The self-assembly of proteins and peptides into amyloid fibrils is connected to over 40 pathological conditions including neurodegenerative diseases and systemic amyloidosis. Diffusible, low molecular weight protein and peptide oligomers that form in the early steps of aggregation appear to be the harmful cytotoxic species in the molecular etiology of these diseases. So far, the structural characterization of these oligomers has remained elusive owing to their transient and dynamic features. We here address, by means of full atomistic replica exchange molecular dynamics simulations, the energy landscape of heptamers of the amyloidogenic peptide NHVTLSQ from the beta-2 microglobulin protein. The simulations totaling 5 ?s show that low molecular weight oligomers in explicit solvent consist of ?-barrels in equilibrium with amorphous states and fibril-like assemblies. The results, also accounting for the influence of the pH on the conformational properties, provide a strong evidence of the formation of transient ?-barrel assemblies in the early aggregation steps of amyloid-forming systems. Our findings are discussed in terms of oligomers cytotoxicity.

de Simone, Alfonso; Derreumaux, Philippe

2010-04-01

317

Low molecular weight chitosan conjugated with folate for siRNA delivery in vitro: optimization studies  

PubMed Central

The low transfection efficiency of chitosan is one of its drawbacks as a gene delivery carrier. Low molecular weight chitosan may help to form small-sized polymer-DNA or small interfering RNA (siRNA) complexes. Folate conjugation may improve gene transfection efficiency because of the promoted uptake of folate receptor-bearing cells. In the present study, chitosan was conjugated with folate and investigated for its efficacy as a delivery vector for siRNA in vitro. We demonstrate that the molecular weight of chitosan has a major influence on its biological and physicochemical properties, and very low molecular weight chitosan (below 10 kDa) has difficulty in forming stable complexes with siRNA. In this study, chitosan 25 kDa and 50 kDa completely absorbed siRNA and formed nanoparticles (?220 nm) at a chitosan to siRNA weight ratio of 50:1. The introduction of a folate ligand onto chitosan decreased nanoparticle toxicity. Compared with chitosan-siRNA, folate-chitosan-siRNA nanoparticles improved gene silencing transfection efficiency. Therefore, folate-chitosan shows potential as a viable candidate vector for safe and efficient siRNA delivery.

Fernandes, Julio C; Qiu, Xingping; Winnik, Francoise M; Benderdour, Mohamed; Zhang, Xiaoling; Dai, Kerong; Shi, Qin

2012-01-01

318

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

319

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

SciTech Connect

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

Ana R. Hortal; Paola Hurtado; Bruno Martinez-Haya; Oliver C. Mullins [Universidad Pablo de Olavide, Seville (Spain). Departamento de Sistemas Fisicos, Quimicos y Naturales

2007-09-15

320

Species variations in the threshold molecular-weight factor for the biliary excretion of organic anions  

PubMed Central

1. The excretion in the bile and urine after intravenous injection of 16 organic anions having molecular weights between 355 and 752 was studied in female rats, guinea pigs and rabbits. 2. These compounds were mostly excreted unchanged, except for three of them, which were metabolized to a slight extent (<7% of dose). 3. The rat excreted all the compounds extensively (22–90% of dose) in the bile. 4. In guinea pigs four of the compounds with mol.wt. 355–403 were excreted in the bile to the extent of 7–16% of the dose, four with mol.wt. 407–465 to the extent of 25–44% and eight compounds with mol.wt. 479–752 to the extent of 44–100%. 5. In rabbits four compounds with mol.wt. 355–465 were excreted in the bile to the extent of 1–8% of the dose, two compounds with mol.wt. 479 and 495 to the extent of 24 and 22%, and six compounds with mol.wt. 505–752 to the extent of 31–94%. 6. These results, together with those of other investigations from this laboratory, are discussed and the conclusion is reached that there is a threshold molecular weight for appreciable biliary excretion (i.e. more than 10% of dose) of anions, which varies with species: about 325±50 for the rat, 400±50 for the guinea pig and 475±50 for the rabbit. 7. Anions with molecular weights greater than about 500 are extensively excreted in the bile of all three species. 8. That proportion of the dose of these compounds which is not excreted in the bile is excreted in the urine, and in the three species, bile and urine are complementary excretory pathways, urinary excretion being greatest for the compounds of lowest molecular weight and tending to decrease with increasing molecular weight. 9. Some implications of this interspecies variation in the molecular-weight requirement for extensive biliary excretion are discussed.

Hirom, P. C.; Millburn, P.; Smith, R. L.; Williams, R. T.

1972-01-01

321

The role of molecular weight and temperature on the elastic and viscoelastic properties of a glassy thermoplastic polyimide  

Microsoft Academic Search

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

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

2002-01-01

322

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

Microsoft Academic Search

Mechanical testing of the elastic and viscoelastic response of an advanced t hermoplastic polyimide (LaRC™-SI) with known variations in molecular weight was performed o ver a range of temperatures below the glass transition temperature. The notched tensile streng th was shown to be a strong function of both molecular weight and temperature, wh ereas stiffness was only a strong function

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

2001-01-01

323

Dilute Solution Properties of High-Molecular-Weight Poly(Isobutyl Methacrylate). Vii. Effect of Centrifuging on Various Parameters.  

National Technical Information Service (NTIS)

Three samples of high-molecular-weight poly(isobuyl methacrylate), designated 937,SW63/0082 and SW62/0298, were all found to be shear dependent. Sample SW62/0298, which has the highest molecular weight, readily dissolved in acetone and methyl ethyl ketone...

E. C. Schramm R. J. Valles

1966-01-01

324

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

325

The influence of sodium hyaluronate molecular weight on protein content according to Lowry and Coomassie blue assays  

Microsoft Academic Search

Sodium hyaluronate (HA) of various molecular weights (MW) were prepared using acid hydrolysis, heat degradation, ultrasonic degradation, and irradiation on the same production batch. The molecular weights were determined using size exclusion chromatography (SEC) with in-line multi-angle laser light scattering (MALLS) and refractive index (RI) detection. The protein content for these samples were determined with the European Pharmacopoeia method for

Claes Melander; Kristoffer Tømmeraas

2008-01-01

326

Synthesis and properties of anionic cellulose ethers: influence of functional groups and molecular weight on flowability of concrete  

Microsoft Academic Search

The suitability of anionic cellulose ethers as superplasticizers and the effect of chemical structure on the fluidity of cement mixtures was investigated. To elucidate the influence of molecular weight and degree of cellulose backbone substitution, cellulose and hydroxyethyl cellulose with molecular weights

Simone Knaus; Birgit Bauer-Heim

2003-01-01

327

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

328

A Convenient Low-Resolution NMR Method for the Determination of the Molecular Weight of Soybean Oil-Based Polymers  

Technology Transfer Automated Retrieval System (TEKTRAN)

By studying a series of soybean oil based polymers, using low resolution nuclear magnetic resonance (NMR) spectroscopy, an easy method to study molecular weight was developed. The relationship between a polymer’s molecular weight and the instrument’s response can be correlated in a linear relations...

329

Demulsification of bitumen emulsions with a high molecular weight mixed alkylene oxide polyol  

SciTech Connect

A process for recovering bitumen from oil-in-water (O/w) emulsions is disclosed wherein water soluble demulsifiers are used. These demulsifiers are polyols of 2 and greater functionality containing predominantly mixed ethylene oxide and propylene oxide wherein the ethylene oxide content of the polyol (by weight) is greater than about 70% but less than about 95%. The molecular weight of these polyols is greater than about 10, to resolve the bituminous petroleum emulsions, the process is carried out between 25 and 1200 c wherein the demulsifier of the invention is contacted with the bituminous emulsion.

Gipson, R.M.; Mccoy, D.R.; Young, K.B.

1982-03-23

330

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

331

The molecular weight and the amino acid and carbohydrate compositions of free secretory component (SC)  

PubMed Central

Free secretory component was isolated from human milk whey using gel filtration and immunosorbent techniques. The purified protein was shown to be homogeneous in the ultracentrifuge and on cellulose acetate, polyacrylamide gel and immunoelectrophoresis. From three different preparations the molecular weight was determined using Archibald's meniscus method. A mean value of 66,000±4500 was found. The S020,w value was calculated to be 4.3 S±0.17 and the D020 value was 5.66±0.08. From these data the molecular weight was calculated to be 67,000±3000. The amino acid composition revealed the absence of methionine from the molecule. The carbohydrate analysis showed the absence of N-acetylgalactosamine and a rather high fucose content. These results are discussed in relation to the carbohydrate composition of secretory IgA and serum IgA. ImagesFIG.1

Van Munster, P. J. J.; Stoelinga, G. B. A.; Clamp, J. R.; Gerding, J. J. Th; Reijnen, J. C. M.; Voss, Maria

1972-01-01

332

Phase behaviour of oat ?-glucan/sodium caseinate mixtures varying in molecular weight.  

PubMed

The isothermal phase behaviour at 5 °C of mixtures of sodium caseinate and oat ?-glucan isolates varying in molecular weight (MW) was investigated by means of phase diagram construction, rheometry, fluorescence microscopy and electrophoresis. Phase diagrams indicated that the compatibility of the ?-glucan/sodium caseinate system increases as ?-glucan MW decreases. Images of mixtures taken at various biopolymer concentrations revealed phase separated domains. Results also revealed that at the state of thermodynamic equilibrium, lower MW samples yielded considerable viscosity in the mixture. At equivalent hydrodynamic volume of ?-glucan in the mixtures, samples varying in molecular weight exhibited similar flow behaviour. A deviation dependent on the protein concentration was observed for the high MW sample in the concentrated regime due to the size of ?-glucan aggregates formed. Results demonstrate that by controlling the structural features of ?-glucan in mixtures with sodium caseinate, informed manipulation of rheological properties in these systems can be achieved. PMID:23265533

Agbenorhevi, Jacob K; Kontogiorgos, Vassilis; Kasapis, Stefan

2012-11-12

333

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

PubMed Central

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

Moldes, Diego; Fernandez-Fernandez, Maria; Sanroman, M. Angeles

2012-01-01

334

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

335

Immunoelectrophoretic characterization of the molecular weight polydispersion of polysaccharides in multivalent bacterial capsular polysaccharide vaccines.  

PubMed

The molecular weight polydispersion of single antigens present in multivalent bacterial capsular polysaccharide vaccines has been characterized by an immunoelectrophoretic method. Chromatographic effluents from Sepharose gel of bacterial capsular polysaccharide vaccines were tested by fused-rocket immunoelectrophoresis and the distribution coefficient (Kd) of each polysaccharide present in the mixture was calculated. The method appeared to be efficient and reproducible. However, different Kd values were obtained by immunoelectrophoretic and chemical or physical analysis of the chromatographic effluents of each single polysaccharide component. The use of this immunoelectrophoretic procedure was extended to the potency control of multivalent meningococcal and pneumococcal polysaccharide vaccines in order to detect changes in the molecular weight polydispersion of each antigen with time. PMID:6833304

Porro, M; Fabbiani, S; Marsili, I; Viti, S; Saletti, M

1983-01-01

336

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

2006-01-30

337

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

PubMed

Primary lung tumors showing features of salivary gland-type neoplasms are extremely rare, and their immunohistochemical profile has been seldom studied. We report two cases of bronchial pleomorphic and mucous gland adenomas and study the expression of markers such as TTF-1 and high molecular weight keratins in these tumors. Both tumors were endobronchial. The pleomorphic adenoma also had a well-circumscribed parenchymal component, with a biphasic morphology composed of epithelial and myoepithelial cells in a background of myxoid and hyaline stroma. The mucous gland adenoma displayed papillary and dilated glandular structures. In both cases, epithelial cells showed strong and diffuse cytoplasmic staining with high molecular weight cytokeratins (cytokeratin 5/6 and keratin 903), and lacked TTF-1 expression. This immunoprofile provides useful clues for the histogenesis of pulmonary benign salivary gland-type adenomas and helps in distinguishing them from primary adenocarcinomas in small biopsy specimens. PMID:16841008

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

2006-02-01

338

Isolation, purification and characterisation of low molecular weight xylanase from Bacillus pumilus SSP-34.  

PubMed

Low molecular weight endo-xylanase from Bacillus pumilus SSP-34 was purified to homogeneity using ion exchange and size exclusion chromatographies. Xylanases were isolated by novel purification protocol which includes the use of anion exchange matrix such as DEAE Sepharose CL 6B with less affinity towards enzyme protein. The purified B. pumilus SSP-34 have a molecular weight of 20 kDa, with optimum pH and temperature at 6.0 and 50 °C, respectively. The enzyme was stable at 50 °C for 30 min. It showed remarkable stability at pH values ranging from 4.5 to 9 when the reaction was carried out at 50 °C. K (m) and V (max) values, determined with oats spelts xylan were 6.5 mg ml?¹ and 1,233 ?mol min?¹ mg?¹ protein, respectively, and the specific activity was 1,723 U mg?¹. PMID:22350873

Subramaniyan, S

2012-02-17

339

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

PubMed

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

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

2012-04-01

340

A novel low molecular weight hemorrhagic toxin from Trimeresurus flavoviridis (Vorojima) venom.  

PubMed

A low molecular weight hemorrhagic toxin, LMHT, was isolated from the venom of Trimeresurus flavoviridis from Yorojima using Q-Sepharose column chromatography. The purified hemorrhagic toxin was homogeneous by disc polyacrylamide gel electrophoresis at pH 8.3, and Ouchterlony immunodiffusion. LMHT has a molecular weight of 16,500 and possesses hemorrhagic activity. It did not show casein, azocasein, azoalbumin, or TAME (tosyl-L-arginine methyl ester hydrochloride) hydrolytic activities. Hemorrhagic activity was inhibited by EDTA, TEP (tetraethylenepentamine), p-APMSF(p-amidinophenylmethanesulfonylfluoride HCl), and N-bromosuccinimide. The minimum hemorrhagic dose of this hemorrhagic toxin was 7.1 microg/mouse. LMHT induced hydrolysis of the Aa and Bbeta chains of bovine fibrinogen. PMID:12182535

Nikai, Toshiaki; Tateoka, Maki; Komori, Yumiko; Tatematsu, Rieko

2002-08-01

341

Comparison between Airway Responses to High versus Low Molecular Weight Compounds in Occupational Asthma.  

PubMed

Occupational asthma (OA) is a heterogeneous disease, and the characteristics of the sensitizer responsible for OA may induce different clinical, functional, and biological manifestations. We examined the characteristics of 74 patients with OA induced by low molecular weight compounds (LMWC) or by high molecular weight compounds (HMWC) and diagnosed by specific inhalation challenge (SIC). Patients with OA induced by LMWC had a longer occupational exposure before the beginning of symptoms, a lower sputum eosinophilia, and a higher prevalence of late airway response (LAR), in comparison with patients with OA induced by HMWC. Pulmonary function tended to be poorer and atopy tended to be less frequent in LMWC-induced OA than in HMWC-induced OA. These data confirm and extend previous observations showing that the characteristics of the specific sensitizer inducing OA may determine different clinical, functional, and biological features, probably related to the difference pathogenetic mechanisms underlying these different types of OA. PMID:21747871

Talini, D; Novelli, F; Bacci, E; Dente, F L; De Santis, M; Di Franco, A; Melosini, L; Vagaggini, B; Paggiaro, P L

2011-05-25

342

Determination of molecular weights and monosaccharide compositions in Abelmoschus manihot polysaccharides  

NASA Astrophysics Data System (ADS)

Abelmoschus manihot polysaccharide, AMP-1, AMP-2, AMP-3, and AMP-4, were purified from four kinds of Abelmoschus manihot gum (AMG). The molecular weights and monosaccharide compositions of AMP-1, AMP-2, AMP-3 and AMP-4 were characterized by gel permeation chromatography, Fourier transform-infrared spectroscopy and high performance anion-exchange chromatography with pulsed amperometric detection. Results indicated that the molecular weights of AMP-1, AMP-2, AMP-3, and AMP-4 were approximately 3.91 × 103, 5.36 × 105, 3.87 × 103, and 5.12 × 105 Da, respectively. The Abelmoschus manihot polysaccharide was mainly composed of galactose, glucose and mannose with the molar ratios at 0.29: 1.00: 0.41 (AMP-1), 0.56: 0.13: 1.00 (AMP-2), 0.10: 1.00: 0.11 (AMP-3) and 0.55: 0.17: 1.00 (AMP-4), respectively.

Wang, Xuemei; Wang, Yingying; Wu, Mimi; Zhang, Xiuzhen

2012-09-01

343

Interactions among Hageman factor, plasma prekallikrein, high molecular weight kininogen, and plasma thromboplastin antecedent.  

PubMed

To investigate the earliest steps of the intrinsic clotting pathway, Hageman factor (Factor XII) was exposed to Sephadex gels to which ellagic acid had been adsorbed; Hageman factor was then separated from the gels and studied in the fluid phase. Sephadex-ellagic acid-exposed Hageman factor, whether purified or in plasma, activated plasma thromboplastin antecedent, but only when high molecular weight kininogen was presnet. In the absence of plasma prekallikrein, maximal activation of plasma thromboplastin antecedent was slightly delayed in plasma, a delay not observed with similarly treated purified Hageman factor. Thus, high molecular weight kininogen was needed for expression of Hageman factor's clot-promoting properties and plasma prekallikrein played a minor role in the interaction of ellagic acid-treated Hageman factor and plasma thromboplastin antecedent. PMID:284420

Ratnoff, O D; Saito, H

1979-02-01

344

Interactions among Hageman factor, plasma prekallikrein, high molecular weight kininogen, and plasma thromboplastin antecedent.  

PubMed Central

To investigate the earliest steps of the intrinsic clotting pathway, Hageman factor (Factor XII) was exposed to Sephadex gels to which ellagic acid had been adsorbed; Hageman factor was then separated from the gels and studied in the fluid phase. Sephadex-ellagic acid-exposed Hageman factor, whether purified or in plasma, activated plasma thromboplastin antecedent, but only when high molecular weight kininogen was presnet. In the absence of plasma prekallikrein, maximal activation of plasma thromboplastin antecedent was slightly delayed in plasma, a delay not observed with similarly treated purified Hageman factor. Thus, high molecular weight kininogen was needed for expression of Hageman factor's clot-promoting properties and plasma prekallikrein played a minor role in the interaction of ellagic acid-treated Hageman factor and plasma thromboplastin antecedent.

Ratnoff, O D; Saito, H

1979-01-01

345

Relationship between molecular weight of poly(ethylene)glycol and intermolecular interaction of Taka-amylase A monomers  

Microsoft Academic Search

Dynamic and static light scattering investigations of Taka-amylase A (TAA) protein monomers were done using solutions containing poly(ethylene)glycol (PEG) with molecular weights of 1500, 4000, 8000, and 20000. The anomalies observed in a previous study using a weight of 8000, in which the hydrodynamic TAA monomer radius at a zero protein concentration and the molecular weight of the monomers decreased

Kazuo Onuma; Naoki Furubayashi; Fujiko Shibata; Yoshiko Kobayashi; Sachiko Kaito; Yuki Ohnishi; Koji Inaka

2010-01-01

346

MOLECULAR WEIGHT, ELECTROCHEMICAL AND BIOLOGICAL PROPERTIES OF TUBERCULIN PROTEIN AND POLYSACCHARIDE MOLECULES.  

PubMed

Studies have been made by means of sedimentation in the ultracentrifuge, and by diffusion and electrophoresis, to determine the molecular weights and homogeneity of the tuberculin protein and polysaccharide molecules as found in their natural state in the unchanged filtrates from culture media after growth of tubercle bacilli. These results have been compared with data obtained on fractions isolated by chemical procedures from them or from old tuberculin. By means of electrophoresis in the Tiselius apparatus it was possible to separate the protein from the polysaccharide, as these two fractions occur naturally in the original culture medium filtrates of acid-fast bacilli. The protein from the bovine strain of bacillus proved to be homogeneous in sedimentation (S(20) = 1.6), diffusion (D(20) = 12.0) and electrophoresis, with a molecular weight of about 10,000. The tuberculin polysaccharide isolated in electrophoresis appeared to be practically the same in sedimentation and in precipitin reaction as the polysaccharide isolated by chemical procedure. The latter proved to be homogeneous in sedimentation (S(20) = 1.6) and diffusion (D(20) = 11.0) with a molecular weight of about 9000. A practically homogeneous protein was isolated from the culture filtrate of the human tubercle bacillus H 37 by fractional ammonium sulfate precipitation, with a molecular weight of 32,000 (S(20) = 3.3; D(20) = 8.2). It was electrochemically homogeneous, with an isoelectric point at pH 4.3 and an isoionic point at pH 4.7. It could be dried or frozen with no loss in homogeneity. It was highly antigenic in the precipitin reaction and produced the anaphylactic type of local skin reaction in tuberculous guinea pigs, in contrast to the true tuberculin type of reaction caused by a purified PPD fraction. Furthermore death resulted in tuberculous guinea pigs from intracutaneous injection of exceptionally small amounts. A protein with molecular weight of about 17,000 was isolated from the filtrate from cultures of the timothy bacillus. The nucleic acid originally occurring in old tuberculin (OT) seems to be responsible for the high electrochemical mobility observed. From OT and the PPD made from it, potent but non-antigenic molecules of 16,000 and 9000 weight and with a low content of nucleic acid were isolated. With increase in size these deviated much from the normal compact spherical shape, and aggregation was evident from the tendency toward gel formation. The smallest molecule (9000) was homogeneous (S(20) = 1.0; D(20) = 10.0) and had lost some tuberculin potency. PMID:19870796

Seibert, F B; Pedersen, K O; Tiselius, A

1938-08-31

347

The effects of hydrogen peroxide and sterilization on the structure of ultra high molecular weight polyethylene  

Microsoft Academic Search

The effects of hydrogen peroxide and sterilization on the structure and morphology of medical-grade ultra high molecular weight polyethylene (UHMWPE) were studied. Microstructural changes were induced via gamma irradiation sterilization and were accelerated by aging in hydrogen peroxide. Differential scanning calorimetry, density gradient column, transmission electron microscopy and small-angle X-ray scattering were used to characterize the structure. Upon oxidation, a

M. Goldman; R. Gronsky; G. G. Long; L. Pruitt

1998-01-01

348

Effects of a Low-Molecular-Weight CCR3 Antagonist on Chronic Experimental Asthma  

Microsoft Academic Search

Eosinophils represent one of the main effector cell populations of allergic airway inflammation and allergic bronchial asthma. Their infiltration correlates with many characteristics of the disease, in- cluding airway hyperresponsiveness (AHR) and increased mucus production. CCR-3 is the principle chemokine receptor involved in eosinophil attraction into inflamed tissue. Therefore, antagonizing CCR-3couldbeanovelpromisingapproachtowardasthmatherapy. Weinvestigatedtheeffectofalow-molecular-weightCCR-3antago- nistonestablishedairwayinflammationinachronicmodelofexper- imental bronchial asthma. For this purpose, BALB\\/c

Michael Wegmann; Rolf Goggel; Sarper Sel; Serdar Sel; Klaus J. Erb; Frank Kalkbrenner; Harald Renz; Holger Garn

349

Function of a Low Molecular Weight Peptide from Trichoderma pseudokoningii S38 During Cellulose Biodegradation  

Microsoft Academic Search

The biochemical mechanism for cellulose decomposition by a low molecular weight peptide, named short fiber generating factor\\u000a (SFGF), derived from the culture supernatant of a cellulolytic fungus Trichoderma pseudokoningii S-38, was determined. Sufficient information obtained by biochemical and biophysical studies and combined with observation\\u000a with a scanning electron microscope provided further evidence for the earlier studies that the SFGF had

Wei Wang; Jie Liu; Guanjun Chen; Yingshu Zhang; Peiji Gao

2003-01-01

350

Processes for converting methane to higher molecular weight hydrocarbons via sulfur-containing intermediates  

SciTech Connect

This patent describes a process for converting methane to higher molecular weight hydrocarbons. The process comprising the steps of contacting methane with carbonyl sulfide in the presence of UV light under conditions sufficient to generate Ch/sub 3/SH; and contacting CH/sub 3/SH with a catalyst under conditions sufficient to produce hydrogen sulfide and a mixture of hydrocarbons having at least two carbon atoms.

Han, S.; Palermo, R.E.

1989-09-05

351

Low-Molecular-Weight Fucoidan Promotes Therapeutic Revascularization in a Rat Model of Critical Hindlimb Ischemia  

Microsoft Academic Search

The therapeutic potential of low-molecular-weight (LMW) fu- coidan, a sulfated polysaccharide extracted from brown sea- weed devoid of direct antithrombin effect, was investigated in vitro and in a model of critical hindlimb ischemia in rat. In vitro results showed that LMW fucoidan enhanced fibroblast growth factor (FGF)-2-induced ( 3 H)thymidine incorporation in cultured rat smooth muscle cells. Intravenous injection in

CHARLES-EDOUARD LUYT; ANNE MEDDAHI-PELL ´ E; BENOIT HO-TIN-NOE; SYLVIA COLLIEC-JOUAULT; JEAN GUEZENNEC; LILIANE LOUEDEC; HERV ´ E PRATS; MARIE-PAULE JACOB; MARY OSBORNE-PELLEGRIN; DIDIER LETOURNEUR; JEAN-BAPTISTE MICHEL; CHU X. Bichat

2003-01-01

352

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

353

Production of colloidally stable latices from low molecular weight ethylene–propylene–diene copolymers  

Microsoft Academic Search

The best impact modifiers for coatings and engineering plastics include fixed morphology core-shell particles. For the present work, ethylene–propylene copolymers (EPM) and ethylene–propylene–diene copolymers (EPDM) were chosen, for their good resistance to stringent conditions, like UV-irradiation or high temperatures, to prepare the core of the desired particles.The solution-emulsification technique was used to produce artificial latices based on low molecular weight

Delphine L Tillier; Jan Meuldijk; Cor E Koning

2003-01-01

354

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

355

Orientation softening in the deformation and wear of ultra-high molecular weight polyethylene  

Microsoft Academic Search

Stress-induced anisotropy is an important phenomenon in the plastic deformation of semi-crystalline linear high polymers. The significance of this phenomenon in the wear of ultra-high molecular weight polyethylene (UHMWPE) bearing surfaces in total joint-replacement prostheses is studied in this investigation. Both linear and crosslinked UHMWPE materials were studied by means of a sequential biaxial tensile test and a hip-joint simulator

A. Wang; D. C. Sun; S.-S. Yau; B. Edwards; M. Sokol; A. Essner; V. K. Polineni; C. Stark; J. H. Dumbleton

1997-01-01

356

Effect of hyaluronic acid molecular weight on the morphology of quantum dot–hyaluronic acid conjugates  

Microsoft Academic Search

The morphological analysis of novel quantum dot–hyaluronic acid (QDot-HA) conjugates was carried out with a transmission electron microscope (TEM). Adipic acid dihydrazide-modified HA (HA-ADH) was synthesized and conjugated to quantum dots (QDots) having carboxyl terminal ligands which were activated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (sulfo-NHS). HA molecules with a molecular weight (MW) of 20K, 234K and 3000K were used

Jiseok Kim; Sei Kwang Hahn

2008-01-01

357

Synthesis and characterization of matrix metalloprotease sensitive-low molecular weight hyaluronic acid based hydrogels  

Microsoft Academic Search

Hyaluronic acid is a naturally derived glycosaminoglycan (GAG) involved in biological processes. A low molecular weight hyaluronic\\u000a acid (50 kDa)-based hydrogel was synthesized using acrylated hyaluronic acid. Matrix metalloproteinase (MMP) sensitive hyaluronic\\u000a acid-based hydrogels were prepared by conjugation with two different peptides: cell adhesion peptides containing integrin\\u000a binding domains (Arg-Gly-Asp: RGD) and a cross-linker with MMP degradable peptides to mimic the

Jungju Kim; Giyoong Tae; Kyu Back Lee; Soon Jung Hwang; In Sook Kim; Insup Noh; Kyung Sun

2008-01-01

358

Influence of dispersion procedure on rheological properties of aqueous solutions of high molecular weight PEO  

Microsoft Academic Search

The linear and nonlinear viscoelastic behaviors of poly(ethylene oxide) (PEO) in aqueous media have been investigated as a\\u000a function of concentration and molecular weight. A particular interest has been paid to study the effect of turbulent flow\\u000a under stirring, inducing both shear and elongational stresses, on the rheological behavior of the polymer solutions. The comparison\\u000a of intrinsic viscosity and viscoelastic

Frédéric Bossard; Nadia El Kissi; Alessandra D’Aprea; Fannie Alloin; Jean-Yves Sanchez; Alain Dufresne

2010-01-01

359

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

360

Synthesis of a polypeptide having an ordered structure with a molecular weight approaching that of tropocollagen  

Microsoft Academic Search

e solution in the presence of triethylamine for five days. The polymer which was obtained in an 89% yield after dialysis, did not dis- solve in methanol and only partially (80%) dissolved in water and 50~c CH3COOH. The sedimentation con- stant in Svedbergs (S) of the water-soluble portion N 7 S. The molecular weight, calculated by the empirical formula(2) logS=

V. A. Shibnev; T. P. Chuvaeva; K. T. Poroshin

1968-01-01

361

Radiation cross-linking in ultra-high molecular weight polyethylene for orthopaedic applications  

PubMed Central

The motivation for radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) is to increase its wear resistance to be used as bearing surfaces for total joint arthroplasty. However, radiation also leaves behind long-lived residual free radicals in this polymer, the reactions of which can detrimentally affect mechanical properties. In this review, we focus on the radiation cross-linking and oxidative stability of first and second generation highly cross-linked UHMWPEs developed in our laboratory.

Oral, Ebru; Muratoglu, Orhun K.

2007-01-01

362

Renal filtration, transport, and metabolism of low-molecular-weight proteins: A review  

Microsoft Academic Search

Low-molecular-weight proteins are a heterogenous group of substances which constitute a small but biologically important fraction of total circulating proteins. The group comprises enzymes (for example, ribonuclease, lysozyme), immuno-proteins (for example, light chains of immunoglobulins, ?2 microglobulin), and peptide-hormones (for example, insulin, growth hormone, parathyroid hormone). Despite general recognition that the kidneys play an important role in the plasma turnover

Thomas Maack; Valerie Johnson; Sen T Kau; Jose Figueiredo; Daniel Sigulem

1979-01-01

363

The Nerve Growth Factor: Purification as a 30,000-Molecular-Weight Protein  

Microsoft Academic Search

The nerve growth factor protein was purified over 100-fold from adult mouse salivary glands. The first step was a gel filtration on Sephadex G-100 at pH 7.5 of the aqueous gland extract. After gel filtration, most of the NGF activity was eluted in the 80,000-90,000-molecular-weight region (G-100 pool). The G-100 pool was dialyzed at pH 5.0 and fractionated by CM52

Vincenzo Bocchini; Pietro U. Angeletti

1969-01-01

364

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

365

Low molecular weight heparin-induced skin necrosis: a case report.  

PubMed

Low molecular weight heparins (LMWHs) are the standard agents used for antithrombotic therapy and prophylaxis. Despite their widespread use, reports about adverse effects from LMWHs are very scarce. Heparin-induced skin necrosis at the injection site is a rare adverse effect, more commonly associated with unfractionated heparin (UFH) rather than with LMWH, while its mechanism remains unclear. This paper deals with the enoxaparin induced skin necrosis. PMID:21687550

Katsourakis, Anastasios; Noussios, George; Kapoutsis, George; Chatzitheoklitos, Efthimios

2011-05-30

366

Radiation cross-linking in ultra-high molecular weight polyethylene for orthopaedic applications  

NASA Astrophysics Data System (ADS)

The motivation for radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) is to increase its wear resistance to be used as bearing surfaces for total joint arthroplasty. However, radiation also leaves behind long-lived residual free radicals in this polymer, the reactions of which can detrimentally affect mechanical properties. In this review, we focus on the radiation cross-linking and oxidative stability of first and second generation highly cross-linked UHMWPEs developed in our laboratory.

Oral, Ebru; Muratoglu, Orhun K.

2007-12-01

367

Observation of salt impurities in ultra-high-molecular-weight polyethylene (UHMWPE)  

Microsoft Academic Search

Different direct molded ultra-high-molecular-weight polyethylene (UHMWPE) samples have been investigated using reflective light microscopy and scanning electron microscope techniques (low voltage and variable pressure SEM). On the surfaces as well as throughout the material a—to the best of our knowledge—unknown type of impurities has been identified. X-ray element analysis (EDX) was used to characterise these impurities as sodium chloride and

J. Loos; M. A. Wimmer

1999-01-01

368

Hydroprocessing of narrow-boiling gas oil fractions; Dependence of reaction kinetics on molecular weight  

Microsoft Academic Search

This paper discusses how a heavy gas oil, produced by thermal coking of Athabasca bitumen, was fractionated into six narrow-boiling cuts of nominal 50° C width and a high-boiling residue. The average molecular weights of the fractions ranged from 187 for the lightest fraction to 653 for the high-boiling residue. The six distillate fractions were catalytically hydroprocessed in a 150-mL

Lyle C. Trytten; Murray R. Gray; Emerson C. Sanford

1990-01-01

369

Synthesis of polypropylene with varied microstructure and molecular weights characteristics using supported titanium catalyst system  

Microsoft Academic Search

Propylene polymerizations were conducted in slurry phase batch process using different dialkyldimethoxysilanes as an external\\u000a donor with magnesium dichloride (MgCl2) supported titanium tetrachloride (TiCl4) catalyst having diisobutylphthalate (DIBP) as an internal donor. The dialkyl group of the external donors like dimethyldimethoxysilane\\u000a (DMDMS), diisopropyldimethoxysilane (DIPDMS) and dicyclopentyldimethoxysilane (DCPDMS) were found to influence on the microstructure\\u000a and the molecular weight characteristics of

Priyanshu B. Vyas; Sukhdeep Kaur; Harshad R. Patil; Virendra K. Gupta

2011-01-01

370

Low molecular weight silicic acid – inorganic compound complex as wood preservative  

Microsoft Academic Search

A new wood preservative containing low molecular weight and low-toxicity silicic acid (LWSA) was investigated. To prevent\\u000a environmental pollution with the wood preservative, a silicic acid monomer aqueous solution (SAMS) or colloidal silicic acid\\u000a solution (CSAS) was combined with various metal compounds or boric acid. Agents where SAMS or CSAS was combined with boric\\u000a acid gave good protection against decay

Haruhiko YAMAGUCHI

2002-01-01

371

Low-molecular weight organic compositions of acid waters from vegetable oil soapstocks  

Microsoft Academic Search

Alkaline extracts (soapstocks) from canola, corn, cottonseed, peanut, soybean, and sunflower oil refining were acidified,\\u000a and identities and concentrations of the low-molecular weight organic components of the resulting acid waters were determined\\u000a by gas chromatography, followed by mass spectroscopy, and by high-performance liquid chromatography. The main components of\\u000a each acid water sample, in order of decreasing concentration and after omitting

Steven L. Johansen; Arunthathi Sivasothy; Michael K. Dowd; Peter J. Reilly; Earl G. Hammond

1996-01-01

372

Pre-analytical operating procedures for serum Low Molecular Weight protein profiling  

Microsoft Academic Search

Biological specimen collection and storage are an integral component of serum proteomics research. Although many efforts have been posed to address the effects of pre-analytical procedures, standardized protocols for collection and storage of samples for Low Molecular Weight (LMW) proteome profiling are still needed.Here we report a systematic analysis on the influence of pre-analytical factors [clotting times, temperature and time

Francesco Di Girolamo; Jhessica Alessandroni; Paolo Somma; Fiorella Guadagni

2010-01-01

373

Photochemical Alkylation of Inorganic Selenium in the Presence of Low Molecular Weight Organic Acids  

Microsoft Academic Search

Using a flow-through photochemical reactor and a low pressure mercury lamp as a UV source, alkyl selenium species are formed from inorganic selenium(IV) in the presence of low molecular weight organic acids (LMW acids). The volatile alkyl Se species were cryogenically trapped and identified by GC-MS and GC-ICP-MS. In the presence of formic, acetic, propionic and malonic acids, inorganic selenium(IV)

Xuming Guo; Ralph E. Sturgeon; Z.a Mester; Graeme J. Gardner

2003-01-01

374

Characterization of some Iraqi asphalts. I. Number average molecular weight investigation of Dora and Qaiyarah asphalts  

SciTech Connect

The number average molecular weight (Mn/sup -/) of two Iraqi asphalts has been studied before and after thermal treatment using vapour pressure osmometery. Changes in Mn/sup -/ values after thermal aging were compared with the changes in their physical and mechanical properties. Toluene, benzene, cyclohexane, tetrahydrofuran and carbon tetrachloride were used to fractionate the asphalts. The Mn/sup -/ of each fraction was determined before and after aging.

Al-Jarrah, M.M.F.; Al-Soufi, H.H.; Apikian, R.L.; Al-Saleem, H.I.; Naoom, S.S.

1986-01-01

375

Solution Structure of a Low-Molecular-Weight Protein Tyrosine Phosphatase from Bacillus subtilis  

Microsoft Academic Search

Received 18 July 2005\\/Accepted 14 November 2005 The low-molecular-weight (LMW) protein tyrosine phosphatases (PTPs) exist ubiquitously in prokaryotes and eukaryotes and play important roles in cellular processes. We report here the solution structure of YwlE, an LMW PTP identified from the gram-positive bacteria Bacillus subtilis. YwlE consists of a twisted central four-stranded parallel -sheet with seven -helices packing on both

Huimin Xu; Bin Xia; Changwen Jin

2006-01-01

376

Low-Molecular-Weight Heparin versus Warfarin for Prevention of Recurrent Venous Thromboembolism: A Randomized Trial  

Microsoft Academic Search

. A group of 105 consecutive patients with venographically proved major acute deep vein thrombosis (DVT) were randomized\\u000a in an open prospective study to evaluate the comparative efficacy and safety of a fixed dose of subcutaneous low-molecular-weight\\u000a heparin (LMWH) and warfarin for the prevention of recurrent venous thromboembolism. Four patients developed venographically\\u000a proved recurrent DVT during the 3 months of

S. K. Das; A. T. Cohen; R. A. Edmondson; E. Melissari; V. V. Kakkar

1996-01-01

377

Preparation and characterization of ‘heparinocytes’: erythrocytes with covalently bound low molecular weight heparin  

Microsoft Academic Search

In an attempt to create the possibility of stable, long acting, intravascular anticoagulation, low molecular weight heparin was modified by introducing a sulfhydryl group into the molecule (LMWH-SH). Human erythrocytes were covalently grafted with LMWH-SH by the use of a heterobifunctional coupling reagent which reacts with the SH group of LMWH-SH and surface exposed amino groups of erythrocytes now called

Michele Müller; Linda Büchi; Karin Woodtli; André Haeberli; Jürg H Beer

2000-01-01

378

Extraction of HL-A transplantation antigen in high molecular weight soluble form  

PubMed Central

A crude membrane extract was made from a typed human spleen and half of the product was solubilized by proteolytic methods previously described. The remaining half was treated with starch stearate and sodium dodecylsulphate and the soluble product compared with the first for its HL-A specificity and behaviour on Sephadex G-200. The product of the starch stearate method had a molecular weight in excess of 200,000 and might be a membrane subunit.

Davies, D. A. L.; Colombani, J.; Viza, D. C.; Hammerling, U.

1971-01-01

379

Sulfate adsorption by variable charge soils: Effect of low-molecular-weight organic acids  

Microsoft Academic Search

Sulfate (SO4\\u000a 2–) movement and transport in soils has received considerable attention in recent years. In most soils, SO4\\u000a 2– coexists with a variety of natural organic compounds, especially organic acids. Studies were conducted to assess the effect\\u000a of low-molecular-weight organic acids (eight aliphatic and five aromatic acids) on SO4\\u000a 2– adsorption by variable charge soils from Chile and Costa

C. E. Martinez; A. W. Kleinschmidt; M. A. Tabatabai

1998-01-01

380

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

Microsoft Academic Search

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

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

2004-01-01

381

Phosphorylation of low-molecular-weight polysaccharide from Enteromorpha linza with antioxidant activity.  

PubMed

In this study, the phosphorylated derivative of low-molecular-weight polysaccharide from Enteromorpha linza was prepared. And then the antioxidant activities of all the samples were investigated including scavenging effects of superoxide and hydroxyl radicals and reducing power. The results of chemical composition, FT-IR spectrum and DSC analysis showed the modifications of polysaccharide were successful. And moreover, the phosphorylated derivative showed excellent antioxidant activity in these three assays, so this derivative needs to be attention in further. PMID:23768575

Wang, Xiaomei; Zhang, Zhongshan; Yao, Qin; Zhao, Mingxing; Qi, Huimin

2013-04-17

382

Thermal conductivity of two binary mixtures of gases of equal molecular weight  

Microsoft Academic Search

The paper reports new measurements of the thermal conductivity of two binary mixtures at a nominal temperature of 27.5°C but over a pressure range. The two systems, N2-CO (three compositions up to 12MPa) and N2O-CO2 (four mixtures up to 4.2 MPa) have been chosen because they consist of molecules of similar structure and equal molecular weight (28.01 and 44.01, respectively).

N. Imaishi; J. Kestin; W. A. Wakeham

1984-01-01

383

Mixing and transport in stars - I. Formalism: momentum, heat and mean molecular weight  

Microsoft Academic Search

The goal of this paper is to derive analytic expressions for the turbulent fluxes of momentum (Reynolds stresses), heat and mean molecular weight. (i) Angular momentum. To solve the angular momentum equation one needs to know the Reynolds stresses Rij, in particular Rphir. It is shown that the latter has the form Rrphi=-2DsSphir- 2DvVphir-D0Omega0- D1Omega+..., where 2Sphir=sinthetar?Omega\\/?r is the shear

V. M. Canuto; F. Minotti

2001-01-01

384

Quantitative analysis of low molecular weight carboxylic acids by capillary zone electrophoresis\\/conductivity detection  

Microsoft Academic Search

Low molecular weight carboxylic acids are separated and quantitated by capillary zone electrophoresis (CZE) with an on-column conductivity detector. The addition of 0.2-0.5 mM TTAB (tetradecyltrimethylammonium bromide) controls the electroosmotic flow so that all carboxylate anions pass through the detector. Unlike other CZE detection methods, conductivity detection shows a direct relationship between retention time and peak area. This confers on

X. Huang; J. A. Luckey; M. J. Gordon; R. N. Zare

1989-01-01

385

Macroamylasaemia following the Infusion of Low Molecular Weight-Hydroxyethyl Starch in Man  

Microsoft Academic Search

In fasted normovolaemic subjects dosed with 400 ml of 14% low molecular weight-hydroxyethyl starch (LMW-HES, Mw 264,000 daltons, Mn 63,000 daltons, Mw\\/Mn = 4.2, MS = 0.43), an increase in the concentration of ?-amylase was observed in blood which exceeded the upper limit of normal (190 U·1-1), and in all cases reached twice the basal value. Concomitant with this elevated

John Milton Mishler; Hans-Karl Dürr

1979-01-01

386

Partial characterization of a non-proteinaceous, low molecular weight antigen of Eimeria tenella  

Microsoft Academic Search

A low molecular weight (LMW) antigen of Eimeria tenella, initially identified using a murine monoclonal antibody (mAb C34F1) raised against E. tenella sporozoites, was partially characterized using enzymatic degradation, solvent extraction, and immunization into various inbred\\u000a lines of mice. The LMW antigen could be isolated using Folch extraction (methanol\\/chloroform\\/water) and the epitope recognized\\u000a by mAb C34F1 was resistant to degradation

John R. Barta; Shan A. Tennyson; Marco L. Schito; Harry D. Danforth; Donald S. Martin

2000-01-01

387

Quality assessment of low molecular weight chitosan coating on sliced red pitayas  

Microsoft Academic Search

This study evaluated the quality of low molecular weight chitosan (LMWC) coating for extending the shelf life and maintaining the quality of sliced red pitayas. Manually sliced red pitayas were treated with aqueous solutions of 0%, 0.2%, 0.5% or 1% LMWC and stored at 8°C. Variations in taste, color and water loss were then assessed. The LMWC coating retarded water

Po-Jung Chien; Fuu Sheu; Hung-Ren Lin

2007-01-01

388

High molecular weight hyaluronan decreases oxidative DNA damage induced by EDTA in human corneal epithelial cells  

PubMed Central

Purpose To investigate the toxic effects of ethylenediaminetetraacetic acid disodium salt (EDTA), a corneal penetration enhancer in topical ophthalmic formulations, on DNA in human corneal epithelial cells (HCEs), and to investigate whether the effect induced by EDTA can be inhibited by high molecular weight hyaluronan (HA). Methods Cells were exposed to EDTA in concentrations ranging from 0.00001 to 0.01% for 60?min, or 30?min high molecular weight HA pretreatment followed by EDTA treatment. The cell viability was measured by the MTT test. Cell apoptosis was determined with annexin V staining by flow cytometry. The DNA single- and double-strand breaks of HCEs were examined by alkaline comet assay and by immunofluorescence microscope detection of the phosphorylated form of histone variant H2AX (?H2AX) foci, respectively. Reactive oxygen species (ROS) production was assessed by the fluorescent probe, 2?, 7?-dichlorodihydrofluorescein diacetate. Results EDTA exhibited no adverse effect on cell viability and did not induce cell apoptosis in human corneal epithelial cells at concentrations lower than 0.01%. However, a significant increase of DNA single- and double-strand breaks was observed in a dose-dependent manner with all the concentrations of EDTA tested in HCEs. In addition, EDTA treatment led to elevated ROS generation. Moreover, 30?min preincubation with high molecular weight HA significantly decreased EDTA-induced ROS generation and DNA damage. Conclusions EDTA could induce DNA damage in HCEs, probably through oxidative stress. Furthermore, high molecular weight HA was an effective protective agent that had antioxidant properties and decreased DNA damage induced by EDTA.

Ye, J; Wu, H; Wu, Y; Wang, C; Zhang, H; Shi, X; Yang, J

2012-01-01

389

Low molecular weight Cooperia oncophora antigens. Potential to discriminate between susceptible and resistant calves after infection  

Microsoft Academic Search

The recognition of low molecular weight proteins by sera obtained during a single oral (primary) infection with 100 000 3rd-stage Cooperia oncophora larvae was studied in calves. Three groups of 6 or 7 calves were selected based on different egg excretion patterns. SDS-gel electrophoresis of adult Cooperia antigen under reducing conditions, followed by Western blotting, revealed that resistance of individual

P. M. Van Diemen; H. W. Ploeger; M. G. B. Nieuwland; F. W. Rietveld; M. Eijsker; F. N. J. Kooijman; A. Kloosterman; H. K. Parmentier

1997-01-01

390

Low-Molecular-Weight Heparin Should Replace Unfractionated Heparin in the Management of Acute Coronary Syndromes  

Microsoft Academic Search

Acute coronary syndromes (unstable angina and non–Q-wave myocardial infarction) are caused by the rupture of an atherosclerotic plaque, platelet activation, and fibrin deposition, resulting in thrombosis. Aspirin and unfractionated heparin (UFH) have traditionally been the treatment of choice in patients with acute coronary syndromes. Low-molecular-weight heparins (LMWHs) offer potential advantages over UFH and have been shown to be equally effective

Peter J. Zed

1999-01-01

391

Properties of self-reinforced ultra-high-molecular-weight polyethylene composites  

Microsoft Academic Search

The physical properties of ultra-high-molecular-weight polyethylene (UHMWPE) fibre\\/UHMWPE matrix composites have been characterized. It was found that the tensile strength and modulus, and creep resistance, were significantly increased after incorporating UHMWPE fibres into a UHMWPE matrix. The longitudinal tensile strength of the resulting self-reinforced composite increased with fibre content, according to the law of mixtures. The transverse strength did not

Meng Deng; Shalaby W. Shalaby

1997-01-01

392

Polyethylene glycol-induced mammalian cell hybridization: Effect of polyethylene glycol molecular weight and concentration  

Microsoft Academic Search

The effects of polyethylene glycol (PEG) molecular weight and concentration on mammalian cell hybridization were studied. The peak hybridization-inducing activity with all grades of PEG from 400–6000 was found to occur in the concentration range of 50–55%. However, changes in concentration were seen to have different quantitative effects with different grades of PEG. For monolayer fusions, PEG 1000 at 50%

Richard L. Davidson; Kathleen A. O'Malley; Thomas B. Wheeler

1976-01-01

393

Low molecular weight heparin inhibits tumor necrosis factor a-induced leukocyte rolling  

Microsoft Academic Search

Objective: Heparins may exert several anti-inflam- matory actions. This study investigated the impact of low molecular weight heparin (LMWH) on tumor necrosis factor (TNF)-a-provoked leukocyte rolling, adhesion and extravas- cular accumulation. Materials and methods: Leukocyte-endothelium interactions and tissue accumulation of leukocytes were induced by TNF- a in Balb\\/c mice and analyzed by the use of intravital microscopy in the mouse

M. X. Wan; X. W. Zhang; L. Törkvist; H. Thorlacius

2001-01-01

394

Low molecular weight protamine-functionalized nanoparticles for drug delivery to the brain after intranasal administration  

Microsoft Academic Search

The development of new strategies for enhancing drug delivery to the brain is of great importance in diagnostics and therapeutics of central nervous diseases. Low-molecular-weight protamine (LMWP) as a cell-penetrating peptide possesses distinct advantages including high cell translocation potency, absence of toxicity of peptide itself, and the feasibility as an efficient carrier for delivering therapeutics. Therefore, it was hypothesized that

Huimin Xia; Xiaoling Gao; Guangzhi Gu; Zhongyang Liu; Ni Zeng; Quanyin Hu; Qingxiang Song; Lei Yao; Zhiqing Pang; Xinguo Jiang; Jun Chen; Hongzhuan Chen

2011-01-01

395

Photocuring of stimulus responsive membranes for controlled-release of drugs having different molecular weights  

Microsoft Academic Search

Intelligent drug delivery membranes were prepared by photocuring poly(acrylic acid) coatings onto poly(2-hydroxyethyl methacrylate) membranes each with model drugs of different molecular weights being incorporated. pH-responsive release behaviours of the model drugs which included sodium salicylate, nicotinamide, nicotinic acid, methylene blue, brilliant green and crystal violet were investigated. Only the membrane with methylene blue incorporated showed a clear pH-responsive release

Loo-Teck Ng; Hiroshi Nakayama; Isao Kaetsu; Kumao Uchida

2005-01-01

396

Production of chloroform and other low molecular-weight halocarbons by some species of macroalgae  

Microsoft Academic Search

The production of volatile low-molecular-weight halocarbons by macroalgae was investigated at a site on the west coast of Scotland. Levels of CH31, CH,Br,, CHBr,, CHBr,Cl, CHBrCl,, and CHC13 were elevated in beds of Laminaria digitata. Storage tests on 11 common species of brown, green, and red seaweeds indicated release of some or all of these compounds. Estimates of production rates

P. D. NIGHTINGALE; G. MALIN; P. S. LISS

1995-01-01

397

Individual Characteristics and Quitting in Apprentices Exposed to High-molecular-weight Agents  

Microsoft Academic Search

To determine whether specific immunological sensitization (SIS) and symptoms of allergy are associated with quitting apprentice- ships with exposure to high-molecular-weight (HMW) agents. In a cohort study of 769 apprentices starting career programs in ani- mal health technology (AHT), pastry-making (PM), and dental hy- giene technology (DHT), health status was assessed at baseline and yearly for up to 44 mo.

EDUARD MONSÓ; JEAN-LUC MALO; CLAIRE INFANTE-RIVARD; HEBERTO GHEZZO; MICHÈLE MAGNAN; CAROLE TRUDEAU; DENYSE GAUTRIN

398

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

399

Low-molecular-weight inhibitors of bacterial DNA-dependent RNA polymerase  

Microsoft Academic Search

The review considers low-molecular-weight inhibitors of bacterial RNA polymerase (RNAP), including classical agents and new\\u000a compounds lacking clinical application as antibiotics thus far. Recent progress in the field is due to structural studies.\\u000a Structural information, together with biochemical data, sheds light on the mechanism of action of the inhibitors, such as\\u000a rifampicin, sorangicin, tagetitoxin, streptolygidin, and microcin J25. In turn,

S. D. Zorov; J. V. Yuzenkova; K. V. Severinov

2006-01-01

400

Low molecular weight EPS II of Rhizobium meliloti allows nodule invasion in Medicago sativa.  

PubMed Central

Effective invasion of alfalfa by Rhizobium meliloti Rm1021 normally requires the presence of succinoglycan, an exopolysaccharide (EPS) produced by the bacterium. However, Rm1021 has the ability to produce a second EPS (EPS II) that can suppress the symbiotic defects of succinoglycan-deficient strains. EPS II is a polymer of modified glucose-(beta-1,3)-galactose subunits and is produced by Rm1021 derivatives carrying either an expR101 or mucR mutation. If the ability to synthesize succinoglycan is blocked genetically, expR101 derivatives of Rm1021 are nodulation-proficient, whereas mucR derivatives of Rm1021 are not. The difference in nodulation proficiency between these two classes of EPS II-producing strains is due to the specific production of a low molecular weight form of EPS II by expR101 strains. A low molecular weight EPS II fraction consisting of 15-20 EPS II disaccharide subunits efficiently allows nodule invasion by noninfective strains when present in amounts as low as 7 pmol per plant, suggesting that low molecular weight EPS II may act as a symbiotic signal during infection. Images Fig. 1 Fig. 2

Gonzalez, J E; Reuhs, B L; Walker, G C

1996-01-01

401

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

DOEpatents

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

Mattes, Benjamin R. (Sante Fe, NM); Wang, Hsing-Lin (Los Alamos, NM)

2000-01-01

402

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

DOEpatents

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

Mattes, Benjamin R. (Santa Fe, NM); Wang, Hsing-Lin (Los Alamos, NM)

1999-11-09

403

Acceptability of low molecular weight heparin thromboprophylaxis for inpatients receiving palliative care: qualitative study  

PubMed Central

Objective To find out what inpatients with advanced cancer who are receiving palliative care think about the effect of thromoprophylaxis on overall quality of life. Design Qualitative study using audiotaping of semistructured interviews. Setting Regional cancer centre in Wales. Participants 28 inpatients with advanced metastatic cancer receiving palliative care and low molecular weight heparin. Main outcome measures Recurring themes on the effect of thromboprophylaxis on overall quality of life. Results Major emerging themes showed that patients knew about the risks of venous thromboembolism and the purpose of treatment with heparin. Media coverage had raised awareness about venous thromboembolism, and many had previous experience of thromboprophylaxis. All found low molecular weight heparin an acceptable intervention, and many said that it improved their quality of life by giving them a feeling of safety and reassurance. Antiembolic stockings were considered uncomfortable and had a negative impact on quality of life. Patients were concerned that because they had advanced disease they might not be eligible for thromboprophylaxis. Conclusion Low molecular weight heparin is acceptable to inpatients with advanced cancer receiving palliative care and has a positive impact on overall quality of life. Antiembolic stockings are an unacceptable intervention in this patient group. Guidelines on thromboprophylaxis are urgently needed for palliative care inpatient units and hospices.

Noble, S I R; Nelson, A; Turner, C; Finlay, I G

2006-01-01

404

Isolation of low molecular weight metal binding proteins from growth plate chondrocytes  

SciTech Connect

Matrix vesicles (MV), cell derived structures responsible for the induction of mineral formation in the extracellular matrix of cartilage and other calcified tissues have previously been shown to contain high concentrations of zinc. In the present study, the intracellular source of MV Zn was investigated. Crude homogenates of chicken epiphyseal growth plates were centrifuged at 100,000 g and the supernatant fractionated by ultrafiltration. The high molecular weight fraction was found to contain 53% of the total An and 80% of the protein. However, the low molecular weight fraction had the highest specific Zn content. Since Zn was not detected in expressed extracellular fluid, the soluble Zn-binding proteins must be derived from the chondrocyte cytosol. Cytosolic proteins obtained from isolated chondrocytes were fractionated on a Sephedex G-75 column. At least two proteins showing low absorbance at 280 nm and high Zn content were observed in the low molecular weight fractions. The results suggest that metallothionein-like proteins are important in the cellular metabolism of metals essential to the normal mineralization of calcified tissues.

Sauer, G.R.; Wuthier, R.E. (Univ. of South Carolina, Columbia (United States))

1991-03-11

405

Low molecular weight silicones are widely distributed after a single subcutaneous injection in mice.  

PubMed Central

To examine the distribution of low molecular weight silicones in body organs, separate groups of female CD-1 mice were injected with either breast implant distillate composed primarily of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and tetradecamethylcycloheptasiloxane or a polydimethylsiloxane oil containing low molecular weight linear siloxanes. Mice were injected subcutaneously in the suprascapular area and killed at different times. Levels of individual low molecular weight silicones were measured in 10 different organs (brain, heart, kidney, liver, lung, mesenteric lymph nodes, ovaries, spleen, skeletal muscle, and uterus). In mice treated with the cyclosiloxane mixture and killed at 3, 6, or 9 weeks, highest levels of cyclosiloxanes were found in the mesenteric lymph nodes, ovaries, and uterus, but all organs examined contained cyclosiloxanes. In a cohort killed at 1 year, most organs contained measurable cyclosiloxanes with highest levels in mesenteric lymph nodes, abdominal fat, and ovaries. Of the individual cyclosiloxanes measured, selective retention of decamethylcyclopentasiloxane and dodecamethylcyclohexasiloxane relative to octamethylcyclotetrasiloxane was seen in all organs at all time points studied. Organs from animals receiving the linear siloxane mixture were harvested at 9, 12, and 15 weeks. We found maximum levels in the brain, lungs, and mesenteric lymph nodes, but all other organs contained measurable levels. These data are, to the best of our knowledge, the first demonstration that after a single subcutaneous injection silicones are widely distributed throughout the body and can persist over an extended period. Images Figure 2 Figure 3 Figure 4

Kala, S. V.; Lykissa, E. D.; Neely, M. W.; Lieberman, M. W.

1998-01-01

406

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

407

Ferrous iron chelating property of low-molecular weight succinoglycans isolated from Sinorhizobium meliloti.  

PubMed

Iron is an essential nutrient for nitrogen-fixing legume root nodules, and the chelation of ferrous iron plays an important role in the mobility and availability of iron to the legume. In the present study, we investigated the iron-binding properties of low-molecular weight succinoglycans isolated from the nitrogen-fixing bacterium, Sinorhizobium meliloti. The low-molecular weight succinoglycans comprising three monomers (M1-M3), four dimers (D1-D4), and six trimers (T1-T6) of the succinoglycan repeating unit were purified by various chromatographic techniques. Interestingly, the colorimetric ferrozine method showed that the succinoglycans T6, M3, and D3 demonstrated a ferrous iron chelating ability of 83, 63, and 38 % per mg, respectively. The individual binding constants were determined as 43703, 2313, and 760 M(-1) for succinoglycans T6, M3, and D3 using ultraviolet-visible spectroscopy. The complexation of succinoglycan and ferrous iron can cause structural changes, which were analyzed by circular dichroism spectroscopy. Furthermore, the complex could provide antioxidant activity through an anti-Fenton reaction. These results demonstrate that the low-molecular weight succinoglycans can effectively modulate iron biochemistry as a novel ferrous iron-acquisition system of S. meliloti. PMID:23412708

Cho, Eunae; Choi, Jae Min; Kim, Hwanhee; Tahir, Muhammad Nazir; Choi, Youngjin; Jung, Seunho

2013-02-15

408

Ionic Conductivity of Nanostructured Block Copolymer Electrolytes in the Low Molecular Weight Limit  

NASA Astrophysics Data System (ADS)

Nanostructured block copolymer electrolytes containing an ion-conducting block and a modulus-strengthening block are of interest for applications in solid-state lithium metal batteries. Previous work using symmetric polystyrene-block-poly(ethylene oxide) mixed with a lithium salt has demonstrated that the ionic conductivity increases with increasing molecular weight of the poly(ethylene oxide) block in the high molecular weight regime due to an increase in the width of the conducting channel. Our current study extends the previous work to the low molecular weight limit. Small angle X-ray scattering, differential scanning calorimetry, and ac impedance spectroscopy experiments help identify the opposing forces influencing the conductivity in these materials. We also examine the annealing process for these materials, whose ion transport characteristics are well known to be influenced by sample preparation and thermal history. The conductivity appears to be influenced by the conductive channel width as well as the glass transition temperature of the insulating block, which also plays an important role in the annealing process.

Teran, Alexander; Yuan, Rodger; Gurevitch, Inna; Balsara, Nitash

2013-03-01

409

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

410

Radiation inactivation of membrane proteins: molecular weight estimates in situ and after Triton X-100 solubilization  

SciTech Connect

Target size analysis by radiation inactivation is widely used for molecular weight determination of membrane enzymes and receptors in situ without the need for prior solubilization or purification. However, since most molecular weight data available in the literature on membrane proteins involve the use of detergents for solubilization, the target sizes of membrane proteins in situ and after solubilization by detergent treatment have been compared. Using data from the literature and personal results, three different types of behavior of membrane proteins in presence of detergents were found: (i) uncoupling of subunits; (ii) coupling of protein molecules; and (iii) no major change in quaternary structure. For all these proteins, there is a statistically significant increase in target size of about 24% over the value obtained in situ without detergent. A relatively large body of literature data involving a variety of membrane proteins, membrane types, and irradiation conditions (electron accelerators or /sup 60/Co sources, and proteins irradiated in lyophilized form or frozen solution) was examined, and it was concluded that target sizes of membrane proteins, irradiated in the presence of Trition X-100, should be diminished by a factor of about 24% to obtain the molecular weight value.

Beauregard, G.; Potier, M.

1984-08-01

411

Radiation inactivation of membrane proteins: molecular weight estimates in situ and after Triton X-100 solubilization.  

PubMed

Target size analysis by radiation inactivation is widely used for molecular weight determination of membrane enzymes and receptors in situ without the need for prior solubilization or purification. However, since most molecular weight data available in the literature on membrane proteins involve the use of detergents for solubilization, the target sizes of membrane proteins in situ and after solubilization by detergent treatment have been compared. Using data from the literature and personal results, three different types of behavior of membrane proteins in presence of detergents were found: (i) uncoupling of subunits (electric eel acetylcholinesterase, placental steroid sulfatase, and human nonspecific beta-glucosidase); (ii) coupling of protein molecules (mouse liver neuraminidase, and rat liver insulin receptor regulatory component); and (iii) no major change in quaternary structure (rat liver insulin receptor, kidney gamma-glutamyltransferase, asialoglycoprotein receptor, insulin degrading enzyme, and human leucocyte neuraminidase). For all these proteins, there is a statistically significant increase in target size of about 24% over the value obtained in situ without detergent. A relatively large body of literature data involving a variety of membrane proteins, membrane types, and irradiation conditions (electron accelerators or 60Co sources, and proteins irradiated in lyophilized form or frozen solution) was examined, and it was concluded that target sizes of membrane proteins, irradiated in the presence of Triton X-100, should be diminished by a factor of about 24% to obtain the molecular weight value. PMID:6148906

Beauregard, G; Potier, M

1984-08-01

412

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

SciTech Connect

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

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

1983-09-01

413

Controlled Release of High Molecular Weight Hyaluronic Acid from Molecularly Imprinted Hydrogel Contact Lenses  

Microsoft Academic Search

Purpose  Current dry eye treatment includes delivering comfort agents to the eye via drops, but low bioavailability and multiple administration\\u000a continues to be a barrier to effective treatment. There exists a significant unmet need for devices to treat dry eye and for\\u000a more comfortable contact lenses.\\u000a \\u000a \\u000a \\u000a Methods  Using molecular imprinting strategies with an analysis of biology, we have rationally designed and synthesized

Maryam Ali; Mark E. Byrne

2009-01-01

414

Radiation and chemical crosslinking promote strain hardening behavior and molecular alignment in ultra high molecular weight polyethylene during multi-axial loading conditions  

Microsoft Academic Search

The mechanical behavior and evolution of crystalline morphology during large deformation of eight types of virgin and crosslinked ultra high molecular weight polyethylene (UHMWPE) were studied using the small punch test and transmission electron microscopy (TEM). We investigated the hypothesis that both radiation and chemical crosslinking hinder molecular mobility at large deformations, and hence promote strain hardening and molecular alignment

Steven M. Kurtz; Lisa A. Pruitt; Charles W. Jewett; Jude R. Foulds; Avram A. Edidin

1999-01-01

415

The High and Low Molecular Weight Forms of Hyaluronan Have Distinct Effects on CD44 Clustering*  

PubMed Central

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

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

2012-01-01

416

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

PubMed

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

Butzke, Daniel; Luch, Andreas

2010-01-01

417

Exocytosis from pancreatic ?-cells: mathematical modelling of the exit of low-molecular-weight granule content  

PubMed Central

Pancreatic ?-cells use Ca2+-dependent exocytosis of large dense core vesicles to release insulin. Exocytosis in ?-cells has been studied biochemically, biophysically and optically. We have previously developed a biophysical method to monitor release of endogenous intragranular constituents that are co-released with insulin. This technique involves the expression of ionotropic membrane receptors in the ?-cell plasma membrane and enables measurements of exocytosis of individual vesicles with sub-millisecond resolution. Like carbon fibre amperometry, this method allows fine details of the release process, like the expansion of the fusion pore (the narrow connection between the granule lumen and the extracellular space), to be monitored. Here, we discuss experimental data obtained with this method within the framework of a simple mathematical model that describes the release of low-molecular constituents during exocytosis of the insulin granules. Our findings suggest that the fusion pore functions as a molecular sieve, allowing differential release of low- and high-molecular-weight granule constituents.

Galvanovskis, Juris; Braun, Matthias; Rorsman, Patrik

2011-01-01

418

Acacia senegal gum: continuum of molecular species differing by their protein to sugar ratio, molecular weight, and charges.  

PubMed

The main chemical and physical features of the Acacia senegal exudate gum and its molecular fractions isolated by chromatographies were determined using a wide variety of methods. Three main molecular fractions were isolated after hydrophobic interaction chromatography (HIC) and biochemical analyses confirmed the presence of an arabinogalactan-peptide (FI), an arabinogalactan-protein (FII), and a glycoprotein (FIII) fraction as described commonly in the literature. Further purification of FIII using size exclusion chromatography revealed three distinct populations. A wide molecular weight distribution within each population with the presence of at least two distinct molecular species per population was identified by high performance size exclusion chromatography coupled to on line multi-angle laser light scattering (HPSEC-MALLS). In addition, both sugars content (neutral and uronic acids) and UV profiles revealed that FIII was composed of a continuum of molecular species differing both by their protein-to-sugar ratio and molecular weight. FI and FII had average molecular weight M(w) of 2.86 x 10(5) and 1.86 x 10(6) g.mol(-1), respectively, and a low polydispersity index (M(w)()/M(n) approximately 1.3). The three populations identified in FIII after HIC separation had M(w) of 2.67 x 10(6), 7.76 x 10(5), and 2.95 x 10(5) g.mol(-1) and very low polydispersity indexes (1.13, 1.04, and 1.01). Estimation of the polypeptide backbone length in the three fractions gave 43, 2253, and 4443 amino acid residues, respectively, hydroxyproline (Hyp) and serine being the most prominent residues within FI and FII, Hyp and Asx (asparagine + aspartic acid) within FIII. Secondary structure prediction from circular dichroism data resulted in polyproline II, beta-sheet, and random coil structures for FII and FIII, whereas no secondary structure was identified in FI. The existence of exposed tryptophanyl residues to the solvent was noticed by fluorescence in FII and FIII, tryptophan residues being absent from FI. In addition, 8-5' non cyclic diferulic acid was identified to be covalently linked to carbohydrate moieties of FII. Infrared spectroscopy identified the different vibrations of saccharidic and peptidic bonds with absorbance amplitudes in agreement with sugar and protein elementary analyses. Titration measurements in order to evaluate the number of charges on total Acacia gum and its molecular fractions revealed that 100% of charges came from polysaccharidic moieties (i.e., glucuronic acids) in FI. Charges coming from polysaccharidic moieties were of 91.3% and 37.9% for FII and FIII, respectively, the remaining 8.7% and 62.1% charges in FII and FIII molecular fractions coming from the polypeptidic backbone. PMID:16961328

Renard, Denis; Lavenant-Gourgeon, Laurence; Ralet, Marie-Christine; Sanchez, Christian

2006-09-01

419

Efficient and accurate approximations to the molecular spin-orbit coupling operator and their use in molecular g-tensor calculations  

NASA Astrophysics Data System (ADS)

Approximations to the Breit-Pauli form of the spin-orbit coupling (SOC) operator are examined. The focus is on approximations that lead to an effective quasi-one-electron operator which leads to efficient property evaluations. In particular, the accurate spin-orbit mean-field (SOMF) method developed by Hess, Marian, Wahlgren, and Gropen is examined in detail. It is compared in detail with the ``effective potential'' spin-orbit operator commonly used in density functional theory (DFT) and which has been criticized for not including the spin-other orbit (SOO) contribution. Both operators contain identical one-electron and Coulomb terms since the SOO contribution to the Coulomb term vanishes exactly in the SOMF treatment. Since the DFT correlation functional only contributes negligibly to the SOC the only difference between the two operators is in the exchange part. In the SOMF approximation, the SOO part is equal to two times the spin-same orbit contribution. The DFT exchange contribution is of the wrong sign and numerically shown to be in error by a factor of 2-2.5 in magnitude. The simplest possible improvement in the DFT-SOC treatment [Veff(-2X)-SOC] is to multiply the exchange contribution to the Veff operator by -2. This is verified numerically in calculations of molecular g-tensors and one-electron SOC constants of atoms and ions. Four different ways of handling the computationally critical Coulomb part of the SOMF and Veff operators are discussed and implemented. The resolution of the identity approximation is virtually exact for the SOC with standard auxiliary basis sets which need to be slightly augmented by steep s functions for heavier elements. An almost as efficient seminumerical approximation is equally accurate. The effective nuclear charge model gives results within ~10% (on average) of the SOMF treatment. The one-center approximation to the Coulomb and one-electron SOC terms leads to errors on the order of ~5%. Small absolute errors are obtained for the one-center approximation to the exchange term which is consequently the method of choice [SOMF(1X)] for large molecules.

Neese, Frank

2005-01-01

420

Dextran-lipase conjugates as tools for low molecular weight ligand immobilization in microarray development.  

PubMed

The development of effective array biosensors relies heavily on careful control of the density of surface-immobilized ligands on the transducing platform. In this paper we describe the synthesis of new dextran-lipase conjugates for use in immobilizing low molecular weight haptens onto glass planar waveguides for immunosensor development. The conjugates were synthesized by immobilizing bacterial thermoalkalophilic lipases (Geobacillus thermocatenulatus lipase 2, BTL2) on agarose macroporous beads, followed by covalent coupling to dextran networks of variable molecular weight (1500-40000). The chimeras were immobilized via nonspecific hydrophobic interactions onto glass planar waveguides modified with 1,1,1,3,3,3-hexamethyldisilazane to obtain highly ordered and homogeneous molecular architectures as confirmed by atomic force microscopy. Microcystin LR (MCLR) was covalently bound to the dextran-BTL2 conjugates. The usefulness of this approach in immunosensor development was demonstrated by determining amounts of MCLR down to a few picograms per liter with an automated array biosensor and evanescent wave excitation for fluorescence measurements of attached DyLight649-labeled secondary antibody. Modifying BTL2 with dextrans of an increased molecular weight (>6000) provided surfaces with an increased loading capacity that was ascribed to the production of three-dimensional surfaces by the effect of analyte binding deep in the volume, leading to expanded dynamic ranges (0.09-136.56 ng L(-1)), lower limits of detection (0.007 ± 0.001 ng L(-1)), and lower IC50 values (4.4 ± 0.7 ng L(-1)). These results confirm the effectiveness of our approach for the development of high-performance biosensing platforms. PMID:23819436

Herranz, Sonia; Marciello, Marzia; Olea, David; Hernández, Margarita; Domingo, Concepción; Vélez, Marisela; Gheber, Levi A; Guisán, Jose M; Moreno-Bondi, María Cruz

2013-07-16

421

A Critique of Asphaltene Fluorescence Decay and Depolarization-Based Claims about Molecular Weight and Molecular Architecture  

SciTech Connect

Relying on experimental and theoretical data available from the literature, it is shown that the conclusions derived from measurements of fluorescence decay and depolarization kinetic times as reported in a series of papers over the past decade are egregiously wrong. To start with, the decay time measurements were done with inappropriate instrumentation which resulted in misleading results. Misinterpretation of the results led to the mistaken conclusion that bichromophoric type molecules are absent from petroleum asphaltene and therefore the architecture of the asphaltene molecule features a single condensed cyclic core spiked with some alkyl chains, in spite of irrefutable chemical evidence to the contrary. It was further concluded that if the asphaltene core is a single condensed ring, then the fluorescence depolarization with rotational correlation time method is applicable for the molecular weight determination of asphaltene. This is definitely not so, since, regardless of any other considerations, asphaltene is a mixture of a plethora of different, unknown components, with unknown concentrations along with innumerable different, unknown and some known chromophores portraying widely different absorption coefficients, fluorescence quantum yields, and kinetic decay times. Consequently, asphaltene fluorescence is a highly complex function of the above attributes and as such it is a totally unsuitable property for its molecular weight determination. The injection of an incorrect, single condensed ring core architecture for asphaltene has caused some confusion in asphaltene chemistry that has now hopefully been settled.

Strausz,O.; Safarik, I.; Lown, E.; Morales-Izquierdo, A.

2008-01-01

422

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

PubMed Central

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

1991-01-01

423

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

PubMed

Numerous studies suggest that two-phase morphology and thick interface are separately beneficial to the viscosity reduction and mechanical property maintainence of the matrix when normal molecular weight polymer (NMWP) is used for modification of ultrahigh molecular weight polyethylene (UHMWPE). Nevertheless, it is very difficult to obtain a UHMWPE/NMWP blend which may demonstrate both two-phase morphology and thick interface. In this work, dissipative particle dynamics simulations and Flory-Huggins theory are applied in predicting the optimum NMWP and the corresponding conditions, wherein the melt flowability of UHMWPE can be improved while its mechanical properties can also be retained. As is indicated by dissipative particle dynamics simulations and phase diagram calculated from Flory-Huggins theory, too small Flory-Huggins interaction parameter (?) and molecular chain length of NMWP (N(NMWP)) may lead to the formation of a homogeneous phase, whereas very large interfacial tension and thin interfaces might also appear when parameters N(NMWP) and ? are too large. When these parameters are located in the metastable region of the phase diagram, however, two-phase morphology occurs and interfaces of the blends are extremely thick. Therefore, metastable state is found to be advisable for both the viscosity reduction and mechanical property improvement of the UHMWPE/NMWP blends. PMID:22038460

Gai, Jing-Gang; Zuo, Yuan

2011-10-27

424

New and rapid procedure for the isolation of ultra-high molecular weight eukaryotic DNA  

SciTech Connect

The authors have developed a novel procedure that permits the rapid extraction and isolation of ultra-high molecular weight DNA from avian or mammalian cells using dialysis against a solution of polyethylene glycol (PEG). Cells harvested by centrifugation and washed twice in ice-cold Ca/sup + +/- and Mg/sup + +/-free phosphate buffered saline were resuspended in 5 ml 0.01 M Tris-Cl (pH 8.0); 0.001 M EDTA (TE); sodium dodecyl sulfate and proteinase K were added to final concentrations of 0.1% and 0.1 mg/ml, respectively. After incubation at 37/sup 0/C overnight, the viscous solution was transferred to a mini-collodian bag and concentrated by dialysis against 4-5 changes of 20% PEG in TE over a period of 5 hours at RT. Concentrated samples were desalted by dialysis against fresh TE for two 15 minute intervals. DNA obtained using this procedure gives A/sub 260//A/sub 280/ consistently >1.8. Analysis of DNA size using pulsed field gel electrophoresis revealed a distribution of fragments >500 Kb in length. Further measurements examined were (1) restriction enzyme digestibility, (2) ligation efficiency of restricted DNA, and (3) cloning efficiency using the lambda vector Ch21A. This novel methodology offers a valuable alternative protocol for rapid purification of ultrahigh molecular weight DNA for various applications in molecular biology.

Longmire, J.L.; Lewis, A.; Meincke, L.J.; Hildebrand, C.E.

1986-05-01

425

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

SciTech Connect

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

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

2005-01-01

426

Molecular-weight factors affecting formation of the OBDD morphology in block copolymer blends.  

PubMed

Block copolymers undergo self-organization when the blocks are sufficiently incompatible, and generate a variety of periodic morphologies in the limit of strong segregation. An equilibrium morphology only recently added to the diblock copolymer phase diagram is the ordered bicontinuous double-diamond (OBDD) morphology, which possess a Pn3m space group. It has been observed over a very narrow composition range (ca. 4 vol%), thereby making it difficult to obtain in pure copolymers. This obstacle can, however, be surmounted by blending a copolymer with one of the parent homopolymers. In the present study, several symmetric poly(styrene-b-isoprene) diblock copolymers varying in molecular weight (M) have been blended with homopolystyrene to produce the OBDD morphology. Transmission electron microscopy is employed here to identify the morphologies in cryosections of each blend and reveals that, at intermediate molecular weights, the OBDD morphology is indeed observed. At low M, near the order-disorder transition, however, a lamellar catenoid or disordered morphology is preferred. At the other extreme, high-M blends are frustrated by molecular entanglements and adopt a cylindrical morphology. PMID:8018993

Spontak, R J; Smith, S D; Ashraf, A

1994-04-01

427

Enrichment of low molecular weight serum proteins using acetonitrile precipitation for mass spectrometry based proteomic analysis.  

PubMed

A rapid acetonitrile (ACN)-based extraction method has been developed that reproducibly depletes high abundance and high molecular weight proteins from serum prior to mass spectrometric analysis. A nanoflow liquid chromatography/tandem mass spectrometry (nano-LC/MS/MS) multiple reaction monitoring (MRM) method for 57 high to medium abundance serum proteins was used to characterise the ACN-depleted fraction after tryptic digestion. Of the 57 targeted proteins 29 were detected and albumin, the most abundant protein in serum and plasma, was identified as the 20th most abundant protein in the extract. The combination of ACN depletion and one-dimensional nano-LC/MS/MS enabled the detection of the low abundance serum protein, insulin-like growth factor-I (IGF-I), which has a serum concentration in the region of 100 ng/mL. One-dimensional sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the depleted serum showed no bands corresponding to proteins of molecular mass over 75 kDa after extraction, demonstrating the efficiency of the method for the depletion of high molecular weight proteins. Total protein analysis of the ACN extracts showed that approximately 99.6% of all protein is removed from the serum. The ACN-depletion strategy offers a viable alternative to the immunochemistry-based protein-depletion techniques commonly used for removing high abundance proteins from serum prior to MS-based proteomic analyses. PMID:18803344

Kay, Richard; Barton, Chris; Ratcliffe, Lucy; Matharoo-Ball, Balwir; Brown, Pamela; Roberts, Jane; Teale, Phil; Creaser, Colin

2008-10-01

428

STUDIES ON THE MOLECULAR WEIGHT OF DIPHTHERIA TOXIN, ANTITOXIN, AND THEIR REACTION PRODUCTS  

PubMed Central

Purified diphtheria antitoxic horse pseudoglobulin has been prepared which is homogeneous by sedimentation, diffusion, and electrophoresis. Immunologically, however, the preparation contains only 43.5 per cent antitoxin specifically precipitable by toxin. The inactive pseudoglobulin remaining after specific precipitation was found to have the same physical and chemical properties as the original antitoxic pseudoglobulin. Although the molecular weight of antitoxin is the same as that of the normal horse serum globulins, the electrophoretic mobility does differ from those normally present. The molecular weight of diphtheria toxin is 70,000 and of antitoxin is 150,000. From ultracentrifuge studies on the two reactants and on mixtures of toxin and antitoxin in the soluble inhibition zones, the average molecular composition of the specific floccules at certain reference points throughout the equivalence zone and the maximum "valence" of toxin and antitoxin with respect to each other have been calculated. The significance of the results has been discussed in relation to antigen-antibody reactions in general and a possible explanation for the exceptional behavior of the toxin-antitoxin reaction in the region of excess antitoxin has been suggested.

Pappenheimer, A. M.; Lundgren, H. P.; Williams, J. W.

1940-01-01

429

Product individuality of commercially available low-molecular-weight heparins and their generic versions: therapeutic implications.  

PubMed

The currently available brand-name low-molecular-weight heparins (LMWHs) in the United States include dalteparin (Pfizer), enoxaparin (Aventis), and tinzaparin (Pharmion). Other products available, in Europe, include certoparin (Novartis), reviparin (Abbott), nadroparin (GlaxoSmithkline), and parnaparin (Alpha-Wasserman). Each of these LMWHs has a characteristic molecular weight profile and biological activity in terms of an anti-FXa and anti-FIIa potency. The mean molecular weight of these drugs ranges from 4.0 kDa to 7.0 kDa and the anti-FXa:anti-FIIa ratio ranges from 1.5 to 3.5. These agents may also be characterized by the presence of specific chemical end groups such as 2-O-sulfo-4-enepyranosuronic acid at the nonreducing terminus (enoxaparin) or 2,5-anhydro-D-mannose at the reducing terminus (dalteparin). Further, the component oligosaccharide chains exhibit product-specific distribution profiles. It is now widely accepted that individual LMWHs are chemically unique agents and cannot be interchanged therapeutically. Each commercial LMWH has been individually developed for specific clinical indications, which are dose and product dependent. Recently, several generic LMWHs have become available in India (Cutenox and Markaparin) and South America (dilutol, clenox, dripanina), and three companies have filed for regulatory approval of a generic version of enoxaparin in the United States. As the primary aim of a generic drug is to reduce cost without compromising patient care, a generic drug is required to be chemically and biologically equivalent to the pioneer drug. Because LMWHs represent complex natural mucopolysaccharide drugs that have undergone chemical and enzymatic modifications, physicochemical and biological information in addition to molecular weight and anti-FXa:anti-FIIa ratio should be used to determine generic equivalency to the branded drug. We have utilized a previously reported approach to systematically compare three generic versions of enoxaparin obtained from India and Brazil with the branded enoxaparin (Lovenox) available in the United States. Testing included molecular and structural profiling, evaluation in clot-based and amidolytic anti-FXa and anti-FIIa assays, and heparinase-I digestion profiles. While the molecular profiles (4.8 +/- 1.8 kD) and anticoagulant potencies as determined by activated partial thromboplastin time (APTT) were comparable for all four agents, the generic products showed variations in the thrombin time (TT) and Heptest assays. Two generic and the branded enoxaparin were readily digested by heparinase-I, losing most of their anticoagulant activity, but one generic product resisted digestion. This may have been due to a unique structural feature in this product. These studies show that, while generic LMWHs may exhibit acceptable molecular weight and anti-FXa profiles, they can exhibit assay-based differences and digestion profiles. Testing in animal models to determine safety, efficacy, and pharmacodynamic parameters may be important to verify equivalence. In order to assure that the generic LMWHs are equivalent to branded LMWHs such that equivalent clinical results are obtained, there is a need to develop clear stepwise guidelines that will establish equivalency in terms of physical, chemical, biochemical, pharmacokinetic, and pharmacodynamic properties for these anticoagulant drugs. PMID:16959680

Maddineni, Jyothi; Walenga, Jeanine M; Jeske, Walter P; Hoppensteadt, Debra A; Fareed, Jawed; Wahi, Rakesh; Bick, Rodger L

2006-07-01

430

Heparin and low-molecular-weight heparin therapy for venous thromboembolism: will unfractionated heparin survive?  

PubMed

Recent improvements in clinical trials methodology and the use of accurate objective tests to detect venous thromboembolism (VTE) have made it possible to carry out a series of randomized trials to evaluate various treatments for VTE. The results of these trials have resolved many of the uncertainties a clinician confronts in selecting the appropriate course of anticoagulant therapy. These trials have shown that the intensity of both initial heparin treatment and long-term anticoagulant therapy must be sufficient to prevent unacceptable rates of recurrence of VTE. Patients with proximal deep vein thrombosis who receive inadequate anticoagulant therapy have a risk of clinically evident, objectively documented recurrent VTE that approaches 20% to 25%. The need for adequate therapy with heparin and the importance of monitoring blood levels of the effect of heparin have been established. The importance of achieving adequate heparinization was suggested by a nonrandomized trial in 1972 and randomized trials in the 1980s have confirmed this finding. Furthermore, randomized trials have demonstrated the importance of achieving adequate heparinization early in the course of therapy. Unfractionated heparin by continuous intravenous infusion has provided an effective therapy for more than half a century, but the need to monitor therapy and establish therapeutic levels is a fundamental problem. It is evident that validated heparin protocols are more successful in establishing adequate heparinization than intuitive ordering by the clinician. However, even with the best of care using a heparin protocol, some patients treated with intravenous heparin will receive subtherapeutic treatment. In this context, subtherapeutic treatment reflects a practical limitation of the use of unfractionated heparin, rather than a poor standard of care. Furthermore, it is recognized that the practical difficulties associated with heparin administration are compounded by the substantive practical difficulties of standardizing activated partial thromboplastin time (aPTT) testing and the therapeutic range. Our findings have emphasized the confounding effect that initial heparin treatment has on long-term outcome. In all trials of long-term treatment, it is imperative that the initial therapy is of adequate intensity and duration; failure to administer adequate initial treatment may lead to a poor outcome that is falsely attributed to the long-term therapy under evaluation. Treatment with low-molecular-weight heparin (LMWH), which does not require monitoring or dose finding, has largely replaced unfractionated heparin for the initial management of VTE. Efficacy in terms of recurrent VTE or extension of thrombus has been at least as good with LMWH as unfractionated heparin and there is evidence that the incidence of major bleeding, heparin-induced thrombocytopenia, and osteoporosis are less with LMWH as compared with unfractionated heparin. Although unfractionated heparin may survive as a treatment option for acute VTE, its use has been largely supplanted by LMWH. PMID:15085462

Hull, Russell D; Pineo, Graham F

2004-02-01

431

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

2013-06-01

432

Low molecular weight chitosan nanoparticulate system at low N:P ratio for nontoxic polynucleotide delivery.  

PubMed

Chitosan, a natural polymer, is a promising system for the therapeutic delivery of both plasmid DNA and synthetic small interfering RNA. Reports attempting to identify the optimal parameters of chitosan for synthetic small interfering RNA delivery were inconclusive with high molecular weight at high amine-to-phosphate (N:P) ratios apparently required for efficient transfection. Here we show, for the first time, that low molecular weight chitosan (LMW-CS) formulations at low N:P ratios are suitable for the in vitro delivery of small interfering RNA. LMW-CS nanoparticles at low N:P ratios were positively charged (?-potential ~20 mV) with an average size below 100 nm as demonstrated by dynamic light scattering and environmental scanning electron microscopy, respectively. Nanoparticles were spherical, a shape promoting decreased cytotoxicity and enhanced cellular uptake. Nanoparticle stability was effective for at least 20 hours at N:P ratios above two in a slightly acidic pH of 6.5. At a higher basic pH of 8, these nanoparticles were unravelled due to chitosan neutralization, exposing their polynucleotide cargo. Cellular uptake ranged from 50% to 95% in six different cell lines as measured by cytometry. Increasing chitosan molecular weight improved nanoparticle stability as well as the ability of nanoparticles to protect the oligonucleotide cargo from nucleases at supraphysiological concentrations. The highest knockdown efficiency was obtained with the specific formulation 92-10-5 that combines sufficient nuclease protection with effective intracellular release. This system attained >70% knockdown of the messenger RNA, similar to commercially available lipoplexes, without apparent cytotoxicity. Contrary to previous reports, our data demonstrate that LMW-CS at low N:P ratios are efficient and nontoxic polynucleotide delivery systems capable of transfecting a plethora of cell lines. PMID:22457597

Alameh, Mohamad; Dejesus, Diogo; Jean, Myriam; Darras, Vincent; Thibault, Marc; Lavertu, Marc; Buschmann, Michael D; Merzouki, Abderrazzak

2012-03-13

433

Interaction between perdeuterated dimyristoylphosphatidylcholine and low molecular weight pulmonary surfactant protein SP-C.  

PubMed

A low molecular weight hydrophobic protein was isolated from porcine lung lavage fluid using silicic acid and Sephadex LH-20 chromatography. The protein migrated with an apparent molecular weight of 5000-6000 on SDS-PAGE under reducing and nonreducing conditions. Gels run under reducing conditions also showed a minor band migrating with a molecular weight of 12,000. Amino acid compositional analysis and sequencing data suggest that this protein preparation contains intact surfactant protein SP-C and about 30% of truncated SP-C (N-terminal leucine absent). The surfactant protein was combined with perdeuterated dimyristoylphosphatidylcholine (DMPC-d54) in multilamellar vesicles. The protein enhanced the rate of adsorption of the lipid at air-water interfaces. The ability of the protein to alter normal lipid organization was examined by using high-sensitivity differential scanning calorimetry (DSC) and 2H nuclear magnetic resonance spectroscopy (2H NMR). The calorimetric measurements indicated that the protein caused a decrease in the temperature maximum (Tm) and a broadening of the phase transition. At a protein concentration of 8% (w/w), the enthalpy change of transition was reduced to 4.4 kcal/mol compared to 6.3 kcal/mol determined for the pure lipid. NMR spectral moment studies indicated that protein had no effect on lipid chain order in the liquid-crystal phase but reduced orientational order in the gel phase. Two-phase coexistence in the presence of protein was observed over a small temperature range below the pure lipid transition temperature. Spin-lattice relaxation times (T1) were not substantially affected by the protein. Transverse relaxation time (T2e) studies suggest that the protein influences slow lipid motions. PMID:2383558

Simatos, G A; Forward, K B; Morrow, M R; Keough, K M

1990-06-19

434

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

SciTech Connect

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

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

2006-01-01

435

Circulating high-molecular-weight RAGE ligands activate pathways implicated in the development of diabetic nephropathy.  

PubMed

The accumulation of advanced glycation end products is thought to be a key factor in the initiation and progression of diabetic nephropathy. Here we determined whether the size of the ligands for the receptor for advanced glycation end products (RAGEs) that were present in the serum of patients with type 2 diabetes modulates their pathogenic potential. Serum was collected from control subjects and patients with type 2 diabetes with varying degrees of renal disease (normo-, micro-, or macroalbuminuria). The titers of the RAGE ligands N-carboxymethyllysine (CML), S100A, S100B, and high-mobility group box 1 (HMGB1) were measured by enzyme-linked immunosorbent assay in serum as well as in pooled size-fractionated serum. We also measured cellular binding of serum fractions to mesangial cells transfected with RAGE and examined the downstream signaling pathways. Circulating CML was increased in patients with type 2 diabetes, whereas HMGB1 was decreased. S100A8, S100BA9, and soluble RAGE were unchanged. The high-molecular-weight (over 50 kDa) serum fraction contained the greatest proportion of RAGE ligands, with all immunoreactivity and cellular binding observed only with serum fractions over 30 kDa. High-molecular-weight serum from macroalbuminuric patients showed greater RAGE binding capacity, modulation of cell-surface RAGE expression, increased phospho-protein kinase C-alpha, and p65 nuclear factor kappaB DNA-binding activity, which were competitively inhibited by soluble RAGE or CML neutralizing antibodies. These data show that ligands that activate RAGE present in the circulation of patients with type 2 diabetes and nephropathy are predominantly of high molecular weight. PMID:20463655

Penfold, Sally A; Coughlan, Melinda T; Patel, Sheila K; Srivastava, Piyush M; Sourris, Karly C; Steer, David; Webster, Diane E; Thomas, Merlin C; MacIsaac, Richard J; Jerums, George; Burrell, Louise M; Cooper, Mark E; Forbes, Josephine M

2010-05-12

436

Low molecular weight chitosan nanoparticulate system at low N:P ratio for nontoxic polynucleotide delivery  

PubMed Central

Chitosan, a natural polymer, is a promising system for the therapeutic delivery of both plasmid DNA and synthetic small interfering RNA. Reports attempting to identify the optimal parameters of chitosan for synthetic small interfering RNA delivery were inconclusive with high molecular weight at high amine-to-phosphate (N:P) ratios apparently required for efficient transfection. Here we show, for the first time, that low molecular weight chitosan (LMW-CS) formulations at low N:P ratios are suitable for the in vitro delivery of small interfering RNA. LMW-CS nanoparticles at low N:P ratios were positively charged (?-potential ~20 mV) with an average size below 100 nm as demonstrated by dynamic light scattering and environmental scanning electron microscopy, respectively. Nanoparticles were spherical, a shape promoting decreased cytotoxicity and enhanced cellular uptake. Nanoparticle stability was effective for at least 20 hours at N:P ratios above two in a slightly acidic pH of 6.5. At a higher basic pH of 8, these nanoparticles were unravelled due to chitosan neutralization, exposing their polynucleotide cargo. Cellular uptake ranged from 50% to 95% in six different cell lines as measured by cytometry. Increasing chitosan molecular weight improved nanoparticle stability as well as the ability of nanoparticles to protect the oligonucleotide cargo from nucleases at supraphysiological concentrations. The highest knockdown efficiency was obtained with the specific formulation 92-10-5 that combines sufficient nuclease protection with effective intracellular release. This system attained >70% knockdown of the messenger RNA, similar to commercially available lipoplexes, without apparent cytotoxicity. Contrary to previous reports, our data demonstrate that LMW-CS at low N:P ratios are efficient and nontoxic polynucleotide delivery systems capable of transfecting a plethora of cell lines.

Alameh, Mohamad; DeJesus, Diogo; Jean, Myriam; Darras, Vincent; Thibault, Marc; Lavertu, Marc; Buschmann, Michael D; Merzouki, Abderrazzak

2012-01-01

437

Improved reproducibility in the determination of the molecular weight of chitosan by analytical size exclusion chromatography  

Microsoft Academic Search

The reproducibility of the determination of the molecular weight of chitosans in the 90–210kDa range (Mn) by analytical size exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) was improved by reducing the salt concentration in the mobile phase from (0.3M acetic acid, 0.2M sodium acetate, and 0.8mM sodium azide) to (0.15M acetic acid, 0.1M sodium acetate, and 0.4mM sodium azide)

Sophie Nguyen; Françoise M. Winnik; Michael D. Buschmann

2009-01-01

438

Study on Different Molecular Weights of Chitosan as an Immobilization Matrix for a Glucose Biosensor  

PubMed Central

Two chitosan samples (medium molecular weight (MMCHI) and low molecular weight (LMCHI)) were investigated as an enzyme immobilization matrix for the fabrication of a glucose biosensor. Chitosan membranes prepared from acetic acid were flexible, transparent, smooth and quick-drying. The FTIR spectra showed the existence of intermolecular interactions between chitosan and glucose oxidase (GOD). Higher catalytic activities were observed on for GOD-MMCHI than GOD-LMCHI and for those crosslinked with glutaraldehyde than using the adsorption technique. Enzyme loading greater than 0.6 mg decreased the activity. Under optimum conditions (pH 6.0, 35°C and applied potential of 0.6 V) response times of 85 s and 65 s were observed for medium molecular weight chitosan glucose biosensor (GOD-MMCHI/PT) and low molecular weight chitosan glucose biosensor (GOD-LMCHI/PT), respectively. The apparent Michaelis-Menten constant () was found to be 12.737 mM for GOD-MMCHI/PT and 17.692 mM for GOD-LMCHI/PT. This indicated that GOD-MMCHI/PT had greater affinity for the enzyme. Moreover, GOD-MMCHI/PT showed higher sensitivity (52.3666 nA/mM glucose) when compared with GOD-LMCHI/PT (9.8579 nA/mM glucose) at S/N>3. Better repeatability and reproducibility were achieved with GOD-MMCHI/PT than GOD-LMCHI/PT regarding glucose measurement. GOD-MMCHI/PT was found to give the highest enzymatic activity among the electrodes under investigation. The extent of interference encountered by GOD-MMCHI/PT and GOD-LMCHI/PT was not significantly different. Although the Nafion coated biosensor significantly reduced the signal due to the interferents under study, it also significantly reduced the response to glucose. The performance of the biosensors in the determination of glucose in rat serum was evaluated. Comparatively better accuracy and recovery results were obtained for GOD-MMCHI/PT. Hence, GOD-MMCHI/PT showed a better performance when compared with GOD-LMCHI/PT. In conclusion, chitosan membranes shave the potential to be a suitable matrix for the development of glucose biosensors.

Ang, Lee Fung; Por, Lip Yee; Yam, Mun Fei

2013-01-01

439

Structure and properties of avian small heat shock protein with molecular weight 25 kDa  

Microsoft Academic Search

The primary structure of chicken small heat shock protein (sHsp) with apparent molecular weight 25 kDa was refined and it was shown that this protein has conservative primary structure 74RALSRQLSSG83 at Ser77 and Ser81, which are potential sites of phosphorylation. Recombinant wild-type chicken Hsp25, its three mutants, 1D (S15D), 2D (S77D+S81D) and 3D (S15D+S77D+S81D), as well as delR mutant with

Olesya O. Panasenko; Alim Seit Nebi; Olesya V. Bukach; Steve B. Marston; Nikolai B. Gusev

2002-01-01

440

Molecular weight and subunit composition of GABA A -ergic compound-sensitive Cl ? , HCO  

Microsoft Academic Search

Molecular weight and subunit composition of Cl?, HCO\\u000a 3\\u000a ?\\u000a , and picrotoxin-stimulated Mg2+-ATPase solubilized with sodium deoxycholate from the plasma membrane fraction of fish brain were studied by gel filtration.\\u000a These enzymes were eluted from a Sephacryl S-300 column as a single peak and corresponded to a ?300 kDa protein with a Stokes\\u000a radius of 5.4 nm. The enzyme-enriched

S. A. Menzikov; O. V. Menzikova

2006-01-01

441

Effect of irradiation on crystallinity and mechanical properties of ultrahigh molecular weight polyethylene  

SciTech Connect

Ultrahigh molecular weight polyethylene (UHMWPE) has been irradiated (0--40 Mrad) with a Co[sup 60] source at room temperature under vacuum. The crystallinity has been investigated by differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). The mechanical properties have been determined at room temperature. A significant increase of heat of fusion can be seen at low irradiation doses, which is attributed to crystallization, caused by chain scission during the process of irradiation. It is also observed that the thickness of the lamellae changes with irradiation dose. The Young's modulus has been improved significantly after irradiation at low doses.

Zhao, Yong; Luo, Yunxia; Jiang, Bingzheng (Academia Sinica, Changchun (China). Changchun Inst. of Applied Chemistry)

1993-12-10

442

Stable transfer of intact high molecular weight DNA into plant chromosomes.  

PubMed Central

In conjunction with an enhanced system for Agrobacterium-mediated plant transformation, a new binary bacterial artificial chromosome (BIBAC) vector has been developed that is capable of transferring at least 150 kb of foreign DNA into a plant nuclear genome. The transferred DNA appears to be intact in the majority of transformed tobacco plants analyzed and is faithfully inherited in the progeny. The ability to introduce high molecular weight DNA into plant chromosomes should accelerate gene identification and genetic engineering of plants and may lead to new approaches in studies of genome organization. Images Fig. 2 Fig. 3 Fig. 4

Hamilton, C M; Frary, A; Lewis, C; Tanksley, S D

1996-01-01

443

Low molecular weight phenols from the bioactive aqueous fraction of Cestrum parqui.  

PubMed

The aqueous fraction of fresh leaves of Cestrum parqui and its organic fractions have been assayed for their phytotoxicity on Lactuca sativa, Lycopersicon esculentum, and Allium cepa. The tests showed that the bioactivity was retained in the organic fractions. Chromatographic processes led to isolation and characterization of the N-(p-carboxymethylphenyl)-p-hydroxybenzamide together with 17 low molecular weight phenols and 2 flavones. The phytotoxicity tests showed a good activity of these compounds on the target species. Comparison of some metabolites with commercial herbicides revealed a major activity of the natural compounds at lower concentrations. PMID:15212454

D'Abrosca, Brigida; DellaGreca, Marina; Fiorentino, Antonio; Monaco, Pietro; Zarrelli, Armando

2004-06-30

444

Synthesis and Evaluation of Pegylated Dendrimeric Nanocarrier for Pulmonary Delivery of Low Molecular Weight Heparin  

Microsoft Academic Search

Purpose  This study tests the hypothesis that pegylated dendrimeric micelles prolong the half-life of low molecular weight heparin\\u000a (LMWH) and increase the drug’s pulmonary absorption, thereby efficacious in preventing deep vein thrombosis (DVT) in a rodent\\u000a model.\\u000a \\u000a \\u000a \\u000a Materials and Methods  Pegylated PAMAM dendrimer was synthesized by conjugating G3 PAMAM dendrimer with methyl ester of polyethylene glycol 2000\\u000a (PEG-2000). Fourier transform infrared (FTIR),

Shuhua Bai; Fakhrul Ahsan

2009-01-01

445

Possible hypoglycemic effect of Aloe vera L. high molecular weight fractions on type 2 diabetic patients  

PubMed Central

Aloe vera L. high molecular weight fractions (AHM) containing less than 10 ppm of barbaloin and polysaccharide (MW: 1000 kDa) with glycoprotein, verectin (MW: 29 kDa), were prepared by patented hyper-dry system in combination of freeze–dry technique with microwave and far infrared radiation. AHM produced significant decrease in blood glucose level sustained for 6 weeks of the start of the study. Significant decrease in triglycerides was only observed 4 weeks after treatment and continued thereafter. No deterious effects on kidney and liver functions were apparent. Treatment of diabetic patients with AHM may relief vascular complications probably via activation of immunosystem.

Yagi, Akira; Hegazy, Sahar; Kabbash, Amal; Wahab, Engy Abd-El

2009-01-01

446

Rheological Properties of Gels from Pyrene Based Low Molecular Weight Gelators  

NASA Astrophysics Data System (ADS)

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.

2008-07-01

447

Density-Functional Theory for Polymer Fluids with Molecular Weight Polydispersity  

NASA Astrophysics Data System (ADS)

We develop a density-functional theory for polydisperse polymer fluids satisfying the Schulz-Flory distribution. The resulting equations are remarkably simple and quickly solved, the computational effort scaling with the polydispersity index, rather than the average molecular weight. Equilibrium, or “living”, polymers enter naturally as very polydisperse samples. We illustrate the importance of polydispersity on colloid stability by investigating interactions between adsorbing and nonadsorbing surfaces. Significant free energy barriers are present in monodisperse samples, but these diminish as the degree of polydispersity increases.

Woodward, Clifford E.; Forsman, Jan

2008-03-01

448

High molecular weight polysaccharide fraction from Aloe vera with immunostimulatory activity  

US Patent & Trademark Office Database

A complex, water soluble polysaccharide fraction having potent immunostimulatory activity isolated from Aloe vera. The polysaccharide fraction has an apparent molecular weight above 2 million daltons. Its major glycosyl components are glucose, galactose, mannose and arabinose. The invention further includes pharmaceutical compositions containing the instant polysaccharide fraction, optionally in combination with acceptable pharmaceutical carriers and/or excipents. These pharmaceutical compositions may be used to provide immunostimulation to an individual in need of such treatment by administering to such an individual an effective amount of the composition. The polysaccharide fraction is also useful as a component of dietary supplements and as a standardization component of commercial Aloe products.

Pasco; David Stanley (Oxford, MS); Pugh; Nirmal Derek Ceri (Oxford, MS); ElSohly; Mahmoud (Oxford, MS); Ross; Samir (Oxford, MS)

2007-03-27

449

Detection of low-molecular-weight domoic acid using surface plasmon resonance sensor  

Microsoft Academic Search

An immunosensor based on surface plasmon resonance (SPR) was used for the detection of a low-molecular-weight analyte, domoic acid (DA) (MW 310g\\/mol), using an inhibition assay. A novel surface functionalization method was developed to chemically immobilize DA molecules onto a gold-coated SPR chip functionalized with mixed oligo(ethylene glycol) (OEG) self-assembled monolayers (SAMs), where the long-chain HS(CH2)11(C2H5O)6NH2 thiol served as a

Qiuming Yu; Shengfu Chen; Allen D. Taylor; Ji?í Homola; Bertold Hock; Shaoyi Jiang

2005-01-01

450

Isolation and characterization of low-molecular-weight chromium-binding substance (LMWCr) from chicken liver.  

PubMed

Chromodulin (also known as low-molecular-weight chromium-binding substance, LMWCr) is a chromium-binding oligopeptide proposed to play a role in insulin signaling and chromium transport in mammals. This laboratory has isolated and purified this material from a non-mammalian source, an avian. Spectroscopic and physical characterization of the isolated material suggests the material is an oligopeptide with a multinuclear chromium assembly bridged via asparatate and glutamate residues very similar to its mammalian counterparts. The isolated material also possesses a biological activity similar to other LMWCr isolates. PMID:18769887

Viera, Margarita; Davis-McGibony, C Michele

2008-09-01

451

Determination of polyethylene glycols of different molecular weight in the stratum corneum.  

PubMed

We developed a sensitive method for determination of polyethylene glycols (PEGs) of different molecular weight (MW) in the human stratum corneum (SC) obtained by tape stripping. The analysis is based on derivatization with pentafluoropropionic anhydride (PFPA) and gas chromatography-electron capture detection (GC-ECD). The identification and quantification of PEGs was done using individual oligomers. The method showed to be suitable for studying permeability in normal and impaired skin with respect to MW in the range of 150-600 Da. PMID:15522718

Jakasa, I; Calkoen, F; Kezic, S

2004-11-25