Copper and cadmium complexation by Cylindrospermopsis raciborskii exudates

2016 ◽  
Vol 73 (10) ◽  
pp. 2544-2551 ◽  
Author(s):  
Alessandra Emanuele Tonietto ◽  
Natalia L. Oliveira ◽  
Ana Teresa Lombardi ◽  
Adriano Polpo
Keyword(s):  
Molecular Weight ◽  
Organic Materials ◽  
Weight Fraction ◽  
Cylindrospermopsis Raciborskii ◽  
Acidity Constants ◽  
Metal Ligands ◽  
Ecological Implications ◽  
Cadmium Complexation ◽  
Strength Of Association ◽  
Molecular Weight Fractions

Cylindrospermopsis raciborskii is a potentially toxic cyanobacterium that excretes organic materials which act as ligands for metals. Metal ligands may be characterized for their strength of association, e.g., stability constants, which can be either thermodynamic (K) or conditional (K’). In this research we examined K and K’ for Cu and Cd complexes with three molecular weight fractions (>30 kDa; 30–10 kDa; 10–3 kDa) of the cyanobacteria EOM. Complexation capacities of the excreted organic materials (EOM) for metals were determined at several ionic strengths (1.0 × 10−2, 5.0 × 10−2, 1.0 × 10−1, and 5.0 × 10−1 mol L−1) at pH 6.6 ± 0.1, with ligands for which no data for their acidity constants are available; these constants are thus conditional for this specific pH. Bayesian statistics showed that with a probability of 95–100% the EOM have two different ligands for Cu but only one for Cd, that ligands for Cu were stronger than for Cd (94–100% probability), and that the smallest EOM fraction had the highest strength of association for Cu (logKCuL 13.5). The lowest affinity was obtained for Cd (logKCdL 8.6) complexed to any molecular weight fraction. The present findings have important ecological implications, since the metal–ligand association is dynamic, and together with a diversity of ligands it can act as an environmental metal buffer. As a result, higher metal loads may be necessary for the detection of toxicity.

Some Osmotic Measurements of the Molecular Weight of a High Molecular-Weight Fraction of Rubber Hydrocarbon

1955 ◽  
Vol 28 (2) ◽  
pp. 504-507
Author(s):  
G. W. Drake
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Average Molecular Weight ◽  
Weight Fraction ◽  
Considerable Proportion ◽  
Prolonged Storage ◽  
High Molecular Weight Fraction ◽  
The United Kingdom ◽  
Molecular Weight Fractions ◽  
Temperate Climates

Abstract Fractionation of the rubber hydrocarbon in temperate climates has usually resulted in high molecular-weight fractions, with a molecular weight of the order of one million. Bloomfield has shown that fresh latex contains a considerable proportion of hydrocarbon having an intrinsic viscosity (η) of 10 or over and, therefore, a molecular weight of well over 106. The fractionation technique used by Bloomfield in Malaya has now been applied by the writer to smoked sheet and to F rubber, working in the United Kingdom. No very high molecular-weight fractions were found in the smoked sheet, but the F rubber yielded a fraction of (η)=7.3 and a number average molecular weight 6×106, determined osmometrically. The average molecular weight of natural rubber when freshly prepared is probably well over a million, and includes a substantial portion having a molecular weight of several millions. By the time smoked sheet has reached temperate climates, the high molecular-weight portion has probably been converted to gel. F rubber, presumably because of its different method of preparation, retains the major part of its high molecular-weight material during prolonged storage.

Uptake of Zinc by the Aquatic Larvae of Simulium ornatipes (Diptera : Nematocera)

1978 ◽  
Vol 29 (3) ◽  
pp. 299 ◽  
Author(s):  
JGT Carter ◽  
WL Nicholas
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Free Water ◽  
Weight Fraction ◽  
The Body ◽  
Ion Concentration ◽  
High Molecular Weight Fraction ◽  
Phosphonic Acids ◽  
Calcium Ion Concentration ◽  
Molecular Weight Fractions

The uptake and loss of zinc by the aquatic larvae of the blackfly S. ornatipes was investigated using radioactive 65Zn. Larvae may absorb significant quantities of zinc from solution, and a substantial proportion remains in the body when larvae are transferred to zinc-free water. Uptake is assisted by metabolism, but an increase of the calcium ion concentration, although reducing toxicity, has no effect on uptake, exchange or the loss of zinc. Larvae may be fractionated into 'cuticle', 'high-' and 'low-molecular-weight' fractions, based on solubility in water and 80% (v/v) ethanol. In the cuticle and high-molecular-weight fractions two 'pools' may be identified by dialysis against Na3EDTA -a pool in which zinc is weakly held and exchanges rapidly with the zinc in solution, and one where zinc is held and exchanges slowly. Exposure time, temperature, and external concentration influence the quantity of zinc entering these pools. Washing the cuticle and high-molecular-weight fractions with a series of buffers suggests that zinc is bound by phenolic groups in the cuticle fraction, and by phosphonic acids in the high-molecular-weight fraction. Sulfhydryl groups did not bind a major portion of the zinc.

Impact of dissolved oxygen concentration on membrane filtering resistance and soluble organic matter characteristics in membrane bioreactors

2008 ◽  
Vol 57 (2) ◽  
pp. 161-165 ◽  
Author(s):  
Kyung-Nan Min ◽  
Sarina J. Ergas ◽  
Anna Mermelstein
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Dissolved Oxygen ◽  
Weight Fraction ◽  
Total Resistance ◽  
Soluble Organic Matter ◽  
Aerobic Conditions ◽  
Do Concentration ◽  
The Impact ◽  
Molecular Weight Fractions

This study investigated the impact of dissolved oxygen (DO) concentration on membrane filtering resistance, soluble organic matter (SOM) and extracellular polymeric substance (EPS) characteristics in a membrane bioreactor (MBR). A laboratory-scale MBR was operated under DO limited (0.2 mg L−1 DO) and fully aerobic (3.7 and 5.4 mg L−1 DO) conditions. Membrane filtering resistance was determined for the mixed liquor suspended solids (MLSS) and for resuspended microbial biomass after removing SOM. Regardless of the DO concentration, the cake resistance (Rc) was approximately 95 percent of the total resistance (Rt). The membrane cake resistance was found to decrease significantly after removing the SOM. The total resistance caused by the resuspended biomass was 29 percent of that caused by the MLSS under DO limited conditions, while the total resistance caused by resuspended biomass was 41 to 48 percent of that caused by the MLSS under fully aerobic conditions. Under DO limited conditions, SOM in the MLSS contained a larger amount of high molecular weight compounds, leading to higher cake resistance than under fully aerobic conditions. There was significant variation in the molecular weight fractions of the EPS, with no clear relationship with DO concentration. There was also no distinct relationship between membrane filtering resistance and molecular weight fraction of the EPS.

Antithrombotic Properties Of Low Molecular Weight Heparin Fractions From Porcine Mucosal Heparin

1981 ◽  
Author(s):  
J Choay ◽  
Jean C Lormeau ◽  
Harry L Messmore ◽  
Jawed Fareed ◽  
J Stulc ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Prothrombin Complex Concentrate ◽  
Specific Activity ◽  
Weight Fraction ◽  
Low Molecular Weight ◽  
Prothrombin Complex Concentrates ◽  
Heparin Fractions ◽  
Russell’S Viper ◽  
Molecular Weight Fractions

A previous report from our laboratories has described the extraction and physicochemical properties of a low molecular weight fraction (mol wt 4-8 × 103 daltons) from porcine mucosal heparin (Choay et. al. thrombosis Res 18, 573, 1980). Beside exhibiting a strong anti Xa (>250 u/mg) activity, this product possessed strong antithrombotic properties in a modified rabbit stasis thrombosis model. At a 125 anti Xa u/kg it protected the thrombotic effects of activated prothrombin complex concentrate (20 u/kg) and Prothrombin Complex Concentrate/Russell’s Viper Venom challenge in both the pretreatment and post-treatment regiments. At 1250 anti Xa u/kg SC it also showed antithrombotic effects for various periods. We have also obtained another low molecular weight fraction from porcine mucosal heparin by controlled depolymerization with nitrous acid. This product possessed saccharides with molecular weight ranging 3-6 × 103 daltons and exhibited a specific activity of >200 anti Xa u/mg. At a 125 anti Xa u/kg this product also showed antithrombotic activity against the thrombotic effects of activated prothrombin complex concentrates, prothrombin complex concentrates and Russell’s Viper Venom. In contrast to these two low molecular weight fractions porcine mucosal heparin in identical anti Xa units failed to produce protection against the thrombogenic stimuli. Our studies suggest that low molecular weight heparin fractions with strong anti Xa and antithrombotic activities can be obtained by chemical depolymerization. Furthermore, their biologic properties are found to be similar to the naturally occuring low molecular weight fractions present in native porcine mucosal heparin.

Uptake and metabolism of transferrin and albumin by rat yolk sac placenta

1984 ◽  
Vol 247 (5) ◽  
pp. C409-C414 ◽  
Author(s):  
H. J. McArdle ◽  
P. K. Priscott
Keyword(s):  
Molecular Weight ◽  
Weight Fraction ◽  
Yolk Sac ◽  
Rapid Phase ◽  
Visceral Yolk Sac ◽  
Transferrin Uptake ◽  
Hydrolysis Of ◽  
Molecular Weight Fractions ◽  
Uptake And Metabolism ◽  
Yolk Sac Placenta

The uptake of radiolabeled albumin and transferrin by the rat yolk sac and their subsequent transport to the embryo were studied. Transferrin uptake increases with incubation time whether the results are expressed in terms of the total amount accumulated or per milligram embryo or yolk sac protein, whereas albumin levels increase only in absolute terms. The fate of transferrin and albumin was examined by partitioning 125I into low- and high-molecular-weight fractions. Nearly all the embryonic radioiodine originally derived from transferrin is in the low-molecular-weight fraction, compared with only 60% albumin. These results have been extended by examining the uptake and hydrolysis of transferrin and albumin by the isolated yolk sac. Transferrin is taken up more rapidly than albumin. The release of hydrolyzed transferrin to the incubation medium occurred 40 min after the initiation of incubation, compared with 20 min for albumin. Transferrin uptake by the yolk sac at different transferrin concentrations showed an initial rapid phase followed by a slower linear phase, whereas albumin uptake increased linearly with concentration. There was no competition between the two proteins for uptake. Transferrin was released from the yolk sacs at approximately twice the rate of albumin. Results demonstrate at least two uptake mechanisms in the rat visceral yolk sac, one for transferrin, which probably involves receptor-mediated endocytosis, and one for albumin, by which transferrin can also be transported, which probably involves pinocytotic mechanisms.

scholarly journals Molecular-mass distribution of tundra soils humic substances from the European northeast of Russia

2015 ◽  
Author(s):  
Roman Vasilevitch ◽  
Evgeniy Lodygin ◽  
Vasiliy Beznosikov
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Molecular Mass Distribution ◽  
Weight Fraction ◽  
Fulvic Acids ◽  
Low Molecular Weight ◽  
Tundra Soils ◽  
Molecular Weight Fractions ◽  
Different Molecular Weight ◽  
A Share

It is established that the humic acids (HA) of tundra soils contain three fractions with a different molecular weight: ≥600, 62–83 and 2,6–5,3 kDa; fulvic acids (FA) — one fraction — 1,5–4,4 kDa. The maintenance of a low molecular weight fraction of HA considerably exceeds a share of medium and high molecular weight fractions. Reclamation of tundra surface-gley soils leads to decrease of a share of high molecular weight and to increase of a share of low molecular weight fraction as a part of HA. Correlative dependences between the contents of HA molecular weight fractions with parameters of HA are established. Refs 16. Figs 1. Tables 3.

STRUCTURE AND CHEMICAL CONTENTS OF MUCILAGE CELLS IN PSEUDOLARIX AND ABIES BARK

IAWA Journal ◽  
2015 ◽  
Vol 36 (3) ◽  
pp. 300-310
Author(s):  
Fengping Jia ◽  
Jiayan Luo ◽  
Ryosuke Takahashi ◽  
Chie Uehira ◽  
Shinichi Kitamura ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Average Length ◽  
Weight Fraction ◽  
Ruthenium Red ◽  
Low Molecular Weight ◽  
High Molecular Weight Fraction ◽  
H Nmr ◽  
Molecular Weight Fractions ◽  
Chemical Contents

Mucilage is extruded from the bark of Pseudolarix amabilis and Abies nephrolepis upon injury. The aim of this study was to characterize the structure and chemical contents of mucilage extruded from mucilage cells (MCs) in the bark of these species. A large number of MCs containing translucent or dark materials in their lumina were observed in the secondary phloem of P. amabilis and A. nephrolepis. The translucent or dark materials in MCs stained positive with ruthenium red and PAS, indicating the presence of polysaccharides. The average length and diameter of MC in P. amabilis were 1500 μm and 254 μm, respectively, and the corresponding values for A. nephrolepis were 419 μm and 166 μm. Chemical analysis of low molecular weight fractions prepared from mucilage by HPAEC-PAD showed sucrose, glucose and fructose peaks, and in addition galacturonic acid and fucose peaks. Furthermore, 1H NMR spectra for the high molecular weight fraction showed the signals characteristic of pectin. This demonstrates that the mucilage consists mainly of low molecular weight carbohydrates and high molecular weight polysaccharide pectin.

Studies on the Functionality of Newly Synthesized Fibrinogen after Treatment of Acute Myocardial Infarction with Streptokinase, Increase in the Rate of Fibrinopeptide Release

1993 ◽  
Vol 70 (06) ◽  
pp. 0978-0983 ◽  
Author(s):  
Edelmiro Regano ◽  
Virtudes Vila ◽  
Justo Aznar ◽  
Victoria Lacueva ◽  
Vicenta Martinez ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Molecular Weight ◽  
Steady State ◽  
High Molecular Weight ◽  
Coronary Arteries ◽  
Risk Index ◽  
Weight Fraction ◽  
High Molecular Weight Fraction ◽  
Fibrinopeptide A

SummaryIn 15 patients with acute myocardial infarction who received 1,500,000 U of streptokinase, the gradual appearance of newly synthesized fibrinogen and the fibrinopeptide release during the first 35 h after SK treatment were evaluated. At 5 h the fibrinogen circulating in plasma was observed as the high molecular weight fraction (HMW-Fg). The concentration of HMW-Fg increased continuously, and at 20 h reached values higher than those obtained from normal plasma. HMW-Fg represented about 95% of the total fibrinogen during the first 35 h. The degree of phosphorylation of patient fibrinogen increased from 30% before treatment to 65% during the first 5 h, and then slowly declined to 50% at 35 h.The early rates of fibrinopeptide A (FPA) and phosphorylated fibrinopeptide A (FPAp) release are higher in patient fibrinogen than in isolated normal HMW-Fg and normal fibrinogen after thrombin addition. The early rate of fibrinopeptide B (FPB) release is the same for the three fibrinogen groups. However, the late rate of FPB release is higher in patient fibrinogen than in normal HMW-Fg and normal fibrinogen. Therefore, the newly synthesized fibrinogen clots faster than fibrinogen in the normal steady state.In two of the 15 patients who had occluded coronary arteries after SK treatment the HMW-Fg and FPAp levels increased as compared with the 13 patients who had patent coronary arteries.These results provide some support for the idea that an increased synthesis of fibrinogen in circulation may result in a procoagulant tendency. If this is so, the HMW-Fg and FPAp content may serve as a risk index for thrombosis.

In Vivo Studies on the Inhibition of Coagulation by Fractionated Heparin and by a Heparin Analogue I. Effects of Heparin Fractions

1981 ◽  
Vol 46 (03) ◽  
pp. 612-616 ◽  
Author(s):  
U Schmitz-Huebner ◽  
L Balleisen ◽  
F Asbeck ◽  
J van de Loo
Keyword(s):  
Molecular Weight ◽  
Day Treatment ◽  
Gel Filtration ◽  
Weight Fraction ◽  
In Vivo Studies ◽  
Low Molecular Weight ◽  
High Molecular Weight Fraction ◽  
Platelet Factor ◽  
Heparin Fractions

SummaryHigh and low molecular weight heparin fractions obtained by gel filtration chromatography of sodium mucosal heparin were injected subcutaneously into six healthy volunteers and compared with the unfractionated substance in a cross-over trial. Equal doses of 5,000 U were administered twice daily over a period of three days and heparin activity was repeatedly controlled before and 2, 4, 8 hrs after injection by means of the APTT, the anti-Xa clotting test and a chromogenic substrate assay. In addition, the in vivo effect of subcutaneously administered fractionated heparin on platelet function was examined on three of the volunteers. The results show that s.c. injections of the low molecular weight fraction induced markedly higher anti-Xa activity than injections of the other preparations. At the same time, APTT results did not significantly differ. Unfractionated heparin and the high molecular weight fraction enhanced ADP-induced platelet aggregation and collagen-mediated MDA production, while the low molecular weight fraction hardly affected these assays, but potently inhibited thrombin-induced MDA production. All heparin preparations stimulated the release of platelet Factor 4 in plasma. During the three-day treatment periods, no side-effects and no significant changes in the response to heparin injections were detected.

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