Characterization of Sol and Gel in Hevea Natural Rubber

1997 ◽  
Vol 70 (5) ◽  
pp. 707-713 ◽  
Author(s):  
Jitladda Tangpakdee ◽  
Yasukuki Tanaka
Keyword(s):  
Molecular Weight ◽  
Weight Fraction ◽  
Toluene Solution ◽  
Low Molecular Weight ◽  
Branch Points ◽  
Gel Content ◽  
High Ammonia ◽  
Linear Molecules ◽  
Cis And Trans

Abstract The gel content of rubber from high-ammonia latex (HA-latex) decreased significantly after deproteinization with proteolytic enzyme. The addition of 1–2% ethanol in toluene solution reduced the gel content of rubbers from HA-latex, deproteinized HA-latex (HA-DP) and pale crepe. Transesterification of the rubber in toluene solution with sodium methoxide dissolved the gel fraction. The gel fractions solubilized after transesterification showed molecular weight distribution rich in low molecular-weight fraction. The Huggins k′ constant of the fractionated rubbers from solubilized-gels was in the range of 0.42–0.45, lower than that of the fractionated HA-DP of 0.5–0.8. This indicates that all the branch-points were decomposed by transesterification to form linear molecules. The Mn values of rubber chains assembling the gel was 5.5−8.3×105 by 13C-NMR measurements of the ratio between cis- and trans-isoprene units, which were comparable to the molecular weight between crosslinks, Mc, of 7−11×105 by swelling measurements. These findings suggest that the branching and crosslinks are composed of two types of branch-points, i. e. one by association or aggregation of proteins or oligopeptides at the initiating end and the other by ester linkages including phosphoric ester at the terminal end.

Isolation and Characterization of Human Platelet β-Thromboglobulin

1975 ◽  
Author(s):  
D. S. Pepper ◽  
S. Moore ◽  
J. D. Cash
Keyword(s):  
Molecular Weight ◽  
Plasma Proteins ◽  
Human Platelet ◽  
Weight Fraction ◽  
Human Platelets ◽  
Low Molecular Weight ◽  
Purification Procedure ◽  
Isolation And Characterization

The thrombin released products from washed human platelets were separated by filtration on 4% agarose in 0.15 M NaCl. The high molecular weight PF4 complex was dissociated and re-chromatographed in 0.75 M NaCl. The low molecular weight fraction, including β thromboglobulin and a low MW anti-heparin was freed of plasminogen anti-activator by dissociation and chromatography in pH 3.5 pyridine acetic acid. The anti-activator was irreversibly denatured and albumin was removed in the void volume of the column. A more suitable purification procedure for recovery of all activities was affinity chromatography on heparin-agarose. The anti-activator was excluded and could be obtained free of plasma proteins by Sephadex G-200 chromatography. The βTG eluted at 0.3 M NaCl and the low MW anti-heparin at 1.5 M NaCl. The pure βTG (MW 36,000) was injected into rabbits and the resulting antiserum used to produce a radioimmunoassay for the release reaction in vivo.

Characterization of bioactive cranberry fractions by mass spectrometry

2020 ◽  
Vol 98 (9) ◽  
pp. 589-596 ◽  
Author(s):  
Marie-Claude Denis ◽  
Pascal Dubé ◽  
Stéphanie Dudonné ◽  
Yves Desjardins ◽  
Cristina Matei ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Phenolic Acids ◽  
High Resolution Mass Spectrometry ◽  
Substantial Reduction ◽  
Weight Fraction ◽  
Total Phenolic ◽  
Low Molecular Weight ◽  
Hydroxybenzoic Acids

Increasing evidence indicates that fruits contain functional bio-active compounds that have several preventive and therapeutic health benefits. Our group has recently conducted studies to assess the potential effects of cranberry polyphenolic fractions on intestinal Caco-2/15 epithelial cells and a substantial reduction in oxidative stress and inflammation was observed. The aim of the present work was to determine the polyphenolic species most likely responsible for the observed biological activity. Low, medium, and high molecular weight cranberry fractions were generated with a Sephadex LH-20 column by elution with 60% MeOH, 100% MeOH, and 70% acetone, respectively. The total phenolic content in these fractions was determined by the Folin–Ciocalteu method. A combination of LC–MS and MALDI-TOF methods were used to characterize the nature of polyphenolic compounds in the cranberry extracts. High resolution mass spectrometry was used to generate empirical formulae for the detected species. The low molecular weight fraction was essentially constituted of small phenolic acids (hydroxycinnamic and hydroxybenzoic acids). The medium fraction was mostly composed of anthocyanin, flavonols (quercetin, myricetin, isorhamnetin, kaempferol), procyanidins monomers (epicatechin, catechin), dimers, and few small oligomers. The heavy fraction was devoid of phenolic acids and anthocyanins, and it contained for the most part oligomers and polymers of procyanidins. Proanthocyanidins oligomers up to n = 22 were detected, which is, to our knowledge, the largest individual polymers reported to date. With this approach, it was also possible to distinguish between the A-type and B-type linkages.

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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