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.

Effect of High Molecular Weight Water-Soluble Chitosan on the Trabecular Bone and Thickness in Ovariectomized Rats

2007 ◽  
Vol 29 (3-4) ◽  
pp. 439-449 ◽  
Author(s):  
Han-Jung Chae ◽  
Geun-Youn Lee ◽  
Sun-Kyung Yang ◽  
Do-Sung Kim ◽  
Ki-Jung Yun ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Trabecular Bone ◽  
High Molecular Weight ◽  
Water Soluble ◽  
Ovariectomized Rats

Interaction of Streptococcus mutans Glucosyltransferases with Teichoic Acids

1980 ◽  
Vol 29 (2) ◽  
pp. 376-382
Author(s):  
H. K. Kuramitsu ◽  
L. Wondrack ◽  
M. McGuinness
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Streptococcus Mutans ◽  
Teichoic Acid ◽  
Lipoteichoic Acid ◽  
Water Soluble ◽  
Heat Inactivation ◽  
Teichoic Acids ◽  
Insoluble Glucan

The Streptococcus mutans GS5 glucosyltransferase activities (both water-soluble and -insoluble glucan-synthesizing fractions) were inhibited by purified lipoteichoic acid. In vitro sucrose-dependent colonization of smooth surfaces by strain GS5 was also markedly reduced in the presence of the amphipathic molecules. The inhibition of soluble glucan synthesis by lipoteichoic acid appeared to be competitive with respect to both sucrose and primer dextran T10. These inhibitory effects were dependent on the presence of the fatty acid components of lipoteichoic acid since deacylated lipoteichoic acids did not inhibit glucosyltransferase activity. However, the deacylated molecules did interact with the enzymes since deacylated lipoteichoic acid partially protected the enzyme activity against heat inactivation and also induced the formation of high-molecular-weight enzyme complexes from the soluble glucan-synthesizing fraction. The presence of teichoic acid in high-molecular-weight aggregates of glucosyltransferase isolated from the culture fluids of strain GS5 was suggested by the detection of polyglycerophosphate in these fractions. In addition to strain GS5, two other organisms containing polyglycerophosphate teichoic acids, Lactobacillus casei and Lactobacillus fermentum , were demonstrated to bind glucosyltransferase activity. These results are discussed relative to the potential role of teichoic acid-glucosyltransferase interactions in enzyme binding to the cell surface of S. mutans and the formation of high-molecular-weight enzyme aggregates in the culture fluids of the organism.

scholarly journals High molecular weight SOA formation during limonene ozonolysis: insights from ultrahigh-resolution FT-ICR mass spectrometry characterization

2012 ◽  
Vol 12 (1) ◽  
pp. 2167-2197
Author(s):  
S. Kundu ◽  
R. Fisseha ◽  
A. L. Putman ◽  
T. A. Rahn ◽  
L. R. Mazzoleni
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Homologous Series ◽  
Condensation Reaction ◽  
Reaction Pathways ◽  
Ultrahigh Resolution ◽  
Group Iii ◽  
Group Ii ◽  
Ft Icr

Abstract. The detailed molecular composition of secondary organic aerosols (SOA) from limonene ozonolysis was studied using ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. High molecular weight (MW) compounds (m/z > 300) were found to constitute a significant number fraction of the identified SOA components. Double bond equivalents (DBE = the number of rings plus the number of double bonds) increased with MW. The O:C ratios and relative abundances of compounds decreased with increasing MW. The mass spectra of limonene contain 4 distinct clusters of negative ions: Group I (140 < m/z < 300), Group II (300 < m/z < 500), Group III (500 < m/z < 700) and Group IV (700 < m/z < 850). A number of CH2 and O homologous series of low MW SOA (Group 1) with carbon number 7–15 and oxygen number 3–9 were observed. Their occurrence can be explained with isomerization and elimination reactions of Criegee radicals, reactions between alkyl peroxy radicals, and scission of alkoxy radicals resulting from the Criegee radicals. Additionally, fragmentation analysis and observations of formaldehyde homologous series provide evidence for aerosol growth by the reactive uptake of generated gas-phase carbonyls in limonene ozonolysis. The decreasing O:C ratios between group of compounds indicated the importance of condensation (aldol and esterification) reaction pathways for high MW compound formation. However, the prominent DBE changes of 2 between the groups of compounds and selected fragmentation (MS/MS) analysis of Group II and Group III ions indicated a predominance of non-condensation (hydroperoxide, Criegee and hemi-acetal) reaction pathways. A reaction matrix created with the combination of low MW SOA, hydroperoxides, and Criegee radicals indicated higher frequencies for the hemi-acetal and condensation reaction pathways. Overall, the combined approach confirms the importance of non-condensation reaction pathways over condensation reaction pathways. Among the non-condensation reaction pathways, hemi-acetal reactions appear to be most dominant followed by hydroperoxide and Criegee reactions.

scholarly journals Catalytic Degradation of Chitosan by Supported Heteropoly Acids in Heterogeneous Systems

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1078
Author(s):  
Hang Zhang ◽  
Zhipeng Ma ◽  
Yunpeng Min ◽  
Huiru Wang ◽  
Ru Zhang ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Weight ◽  
Catalytic Activity ◽  
Activated Carbon ◽  
Reaction Time ◽  
High Molecular Weight ◽  
Reaction Temperature ◽  
Water Soluble ◽  
High Catalytic Activity ◽  
High Molecular Weight Chitosan

Several kinds of composite materials with phosphotungstic acid (PTA) as the catalyst were prepared with activated carbon as support, and their structures were characterized. According to the Box–Behnken central combination principle, the mathematical model of the heterogeneous system is established. Based on the single-factor experiments, the reaction temperature, the reaction time, the amount of hydrogen peroxide and the loading capacity of PTA were selected as the influencing factors to study the catalyzed oxidation of hydrogen peroxide and degradation of high molecular weight chitosan. The results of IR showed that the catalyst had a Keggin structure. The results of the mercury intrusion test showed that the pore structure of the supported PTA catalyst did not change significantly, and with the increase of PTA loading, the porosity and pore volume decreased regularly, which indicated that PTA molecules had been absorbed and filled into the pore of activated carbon. The results of Response Surface Design (RSD) showed that the optimum reaction conditions of supported PTA catalysts for oxidative degradation of high molecular weight chitosan by hydrogen peroxide were as follows: reaction temperature was 70 ℃, reaction time was 3.0 h, the ratio of hydrogen peroxide to chitosan was 2.4 and the catalyst loading was 30%. Under these conditions, the yield and molecular weight of water-soluble chitosan were 62.8% and 1290 Da, respectively. The supported PTA catalyst maintained high catalytic activity after three reuses, which indicated that the supported PTA catalyst had excellent catalytic activity and stable performance compared with the PTA catalyst.

Research Note: The Central Domain of High Molecular Weight Glutenin Subunits is Water-Soluble

1999 ◽  
Vol 29 (2) ◽  
pp. 109-112 ◽  
Author(s):  
A.C.A.P.A. Bekkers ◽  
E. de Boef ◽  
A.A. van Dijk ◽  
R.J. Hamer
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Water Soluble ◽  
Research Note ◽  
Glutenin Subunits ◽  
Central Domain

Nitric oxide production by high molecular weight water-soluble chitosan via nuclear factor-κB activation

2000 ◽  
Vol 22 (11) ◽  
pp. 923-933 ◽  
Author(s):  
Hyun-Ja Jeong ◽  
Hyun-Na Koo ◽  
Eun-Young Oh ◽  
Han-Jung Chae ◽  
Hyung-Ryong Kim ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Nuclear Factor Κb ◽  
Water Soluble ◽  
Nitric Oxide Production ◽  
Nuclear Factor ◽  
Oxide Production
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