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

1984 ◽  
Vol 26 (12) ◽  
pp. 1475-1484 ◽  
Author(s):  
James E. Rollings ◽  
Robert W. Thompson
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Product Distribution ◽  
High Molecular Weight Product ◽  
Kinetics Of ◽  
Molecular Weight Product ◽  
Starch Liquefaction

Lignin-Carbohydrate Condensation Product Formation in a Biomimetic Model Pulp Bleaching System

Holzforschung ◽  
2003 ◽  
Vol 57 (4) ◽  
pp. 385-390 ◽  
Author(s):  
C. C. Walker ◽  
T. J. McDonough ◽  
R. J. Dinus ◽  
K.-E. L. Eriksson
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Condensation Product ◽  
Condensation Reaction ◽  
Product Formation ◽  
Water Soluble ◽  
Hydroxyethyl Cellulose ◽  
Pulp Bleaching ◽  
High Molecular Weight Product ◽  
Molecular Weight Product

Abstract Three biomimetic compounds were evaluated for their ability to preferentially degrade lignin in the presence of carbohydrate using two water-soluble polymeric model compounds: lignosulfonate and hydroxyethyl cellulose (HEC). The three biomimetic systems studied were FeSO4, Fe-EDTA and hemoglobin, each in the presence of hydrogen peroxide. When both polymeric substrates were present, a high molecular weight product was observed to form upon addition of H2O2. This high molecular weight product is believed to be the result of a condensation reaction between lignosulfonate and HEC. The condensation product was also observed to form in the absence of biomimetic catalyst. For all reactions, the molecular weight of the condensation product was observed to decrease with increasing reaction time. By altering the ratio of lignosulfonate to HEC, a limit was observed in the relative amount of condensation product formed. The formation of this condensation product is believed to limit the effectiveness of acidic bleaching systems.

scholarly journals Thermal Degradation Kinetics and Modeling Study of Ultra High Molecular Weight Polyethylene (UHMWP)/Graphene Nanocomposite

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1597
Author(s):  
Iman Jafari ◽  
Mohamadreza Shakiba ◽  
Fatemeh Khosravi ◽  
Seeram Ramakrishna ◽  
Ehsan Abasi ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Thermal Degradation ◽  
High Molecular Weight ◽  
Degradation Kinetics ◽  
Graphene Nanosheets ◽  
Thermal Degradation Kinetics ◽  
Graphene Nanocomposites ◽  
Kinetics Of ◽  
Ultra High Molecular Weight

The incorporation of nanofillers such as graphene into polymers has shown significant improvements in mechanical characteristics, thermal stability, and conductivity of resulting polymeric nanocomposites. To this aim, the influence of incorporation of graphene nanosheets into ultra-high molecular weight polyethylene (UHMWPE) on the thermal behavior and degradation kinetics of UHMWPE/graphene nanocomposites was investigated. Scanning electron microscopy (SEM) analysis revealed that graphene nanosheets were uniformly spread throughout the UHMWPE’s molecular chains. X-Ray Diffraction (XRD) data posited that the morphology of dispersed graphene sheets in UHMWPE was exfoliated. Non-isothermal differential scanning calorimetry (DSC) studies identified a more pronounced increase in melting temperatures and latent heat of fusions in nanocomposites compared to UHMWPE at lower concentrations of graphene. Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) revealed that UHMWPE’s thermal stability has been improved via incorporating graphene nanosheets. Further, degradation kinetics of neat polymer and nanocomposites have been modeled using equations such as Friedman, Ozawa–Flynn–Wall (OFW), Kissinger, and Augis and Bennett’s. The "Model-Fitting Method” showed that the auto-catalytic nth-order mechanism provided a highly consistent and appropriate fit to describe the degradation mechanism of UHMWPE and its graphene nanocomposites. In addition, the calculated activation energy (Ea) of thermal degradation was enhanced by an increase in graphene concentration up to 2.1 wt.%, followed by a decrease in higher graphene content.

Degradation kinetics of high molecular weight poly(L-lactide) microspheres and release mechanism of lipid:DNA complexes

2004 ◽  
Vol 93 (10) ◽  
pp. 2573-2584 ◽  
Author(s):  
Mayank M. Patel ◽  
Michelle G. Zeles ◽  
Mark C. Manning ◽  
Theodore W. Randolph ◽  
Thomas J. Anchordoquy
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Degradation Kinetics ◽  
Release Mechanism ◽  
Kinetics Of ◽  
High Molecular Weight Poly

Uptake and Catabolism of 125l-Thrombin by the Rabbit Thoracic Aorta In Vitro: Permeability of the Endothelium, Intima-Media and Adventitial Layers

1984 ◽  
Vol 52 (02) ◽  
pp. 105-111 ◽  
Author(s):  
Mark W C Hatton ◽  
Sue L Moar
Keyword(s):  
Molecular Weight ◽  
Endothelial Cells ◽  
Vessel Wall ◽  
Antithrombin Iii ◽  
High Molecular Weight Product ◽  
Constant Rate ◽  
Molecular Weight Product ◽  
Media Layer ◽  
Extracellular Proteolysis

SummaryThe uptake, distribution and catabolism of 125I-thrombin has been studied in vitro using normal and ballooned (de-endothelialized) aorta segments at 37° C and at 4° C. In addition to rapid uptake by endothelial cells, 125I-thrombin passed at a slower, and yet constant, rate through the endothelium and accumulated in the intima-medial and adventitial layers. The enzyme, however, was not able to cross the adventitia. Passage through the endothelium was probably intercellular rather than due to transcytosis. Uptake by the intima-media layer of ballooned segments was substantially faster (× 2.5) than by the subendothelial (intima-media) region of normal segments. Once associated with the endothelium and the subendothelial layers, 125I-thrombin was catabolized and radioactive products, which were released from the vessel wall, appeared in the incubation medium. Two possible catabolic routes were identified: 1. the enzyme was recovered as a high molecular weight product (i. e. excluded by Sephadex G-200), due to complex formation with an extracellular vessel wall component and/or plasma antithrombin III. 2. Fragments of the enzyme were recovered which were presumably the products of limited, extracellular proteolysis.

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