scholarly journals Structural Changes of Oak Wood Main Components Caused by Thermal Modification

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 485 ◽  
Author(s):  
Ivan Kubovský ◽  
Danica Kačíková ◽  
František Kačík
Keyword(s):  
Structural Changes ◽  
Biological Properties ◽  
Degree Of Polymerization ◽  
Thermal Modification ◽  
Size Exclusion ◽  
Chemical Changes ◽  
Oak Wood ◽  
Degradation Reactions ◽  
Exclusion Chromatography ◽  
Main Components

Thermal modification of wood causes chemical changes that significantly affect the physical, mechanical and biological properties of wood; thus, it is essential to investigate these changes for better utilization of products. Fourier transform infrared spectroscopy and size exclusion chromatography were used for evaluation of chemical changes at thermal treatment of oak wood. Thermal modification was applied according to Thermowood process at the temperatures of 160, 180 and 210 °C, respectively. The results showed that hemicelluloses are less thermally stable than cellulose. Chains of polysaccharides split to shorter ones leading to a decrease of the degree of polymerization and an increase of polydispersity. At the highest temperature of the treatment (210 °C), also crosslinking reactions take place. At lower temperatures degradation reactions of lignin predominate, higher temperatures cause mainly condensation reactions and a molecular weight increase. Chemical changes in main components of thermally modified wood mainly affect its mechanical properties, which should be considered into account especially when designing various timber constructions.

Influence of environment, temperature and time of the thermal modification of ash wood (Fraxinus excelsior L.) on the cellulose weight average degree of polymerization

2021 ◽  
Vol 116 ◽  
pp. 39-45
Author(s):  
Jakub Gawron
Keyword(s):  
Size Exclusion Chromatography ◽  
Degree Of Polymerization ◽  
Thermal Modification ◽  
Average Degree ◽  
Fraxinus Excelsior ◽  
Size Exclusion ◽  
Wood Modification ◽  
Degradation Reactions ◽  
Environment Temperature ◽  
Exclusion Chromatography

Influence of environment, temperature and time of the thermal modification of ash wood (Fraxinus excelsior L.) on the cellulose weight average degree of polymerization . Using the size-exclusion chromatography (HPLC SEC) method, the weight average degree of cellulose polymerization was determined. The polymer was isolated by the Kürschner-Hoffer method from ash wood (Fraxinus excelsior L.). The wood was thermally modified in different environments (nitrogen, steam and air) at 190°C and modification times of 2, 6 and 10 hours. Depending on the anaerobic atmosphere used, the highest values of the weight average degree of cellulose polymerization were obtained for the nitrogen environment, followed by steam and air. The effect of modification time on the weight average degree of polymerization was observed. The highest values were obtained for wood modified at 2 hours, then 6 and 10 hours of modification. The native wood showed the highest degree of polymerization. On the basis of the results obtained, it can be concluded that for the material studied the oxidation and degradation reactions occurring depend on the environment and time for a given temperature of wood modification.

Mimicking of the strength loss in the Vasa: model experiments with iron-impregnated recent oak

Holzforschung ◽  
2013 ◽  
Vol 67 (6) ◽  
pp. 707-714 ◽  
Author(s):  
Shahin Norbakhsh ◽  
Ingela Bjurhager ◽  
Gunnar Almkvist
Keyword(s):  
Average Molecular Weight ◽  
Oxidative Degradation ◽  
Strength Loss ◽  
Size Exclusion ◽  
Pure Oxygen ◽  
Iron Compounds ◽  
Oak Wood ◽  
Degradation Reactions ◽  
Exclusion Chromatography ◽  
Oxidative Processes

Abstract Previous studies of the oak wood of the 17th century warship the Vasa have shown significant changes in the chemical and mechanical properties compared with recent oak. The most important factors contributing to these changes are the incorporation of iron compounds during waterlogging and the uptake of polyethylene glycol (PEG) in the course of the 17 years of preservation treatment. To investigate the effect of iron-dependent oxidative degradation reactions, recent oak wood samples were impregnated with aqueous iron(II) chloride solution (0.1 M) and thereafter exposed to air or pure oxygen at controlled relative humidity in long-term experiments followed by tensile strength (TS) measurements. The iron-impregnated samples exposed to oxygen displayed significant effects already after 1 week and the reduction in TS was ~50% after 1 year. The samples treated with additional PEG displayed less TS reduction, whereas the addition of cysteine had no effect. The size exclusion chromatography of treated samples showed that the average molecular weight of holocellulose had decreased. The results confirm that iron compounds have a detrimental effect in wood and indicate that PEG might act as an antioxidant for the degradation processes. Concerning the Vasa, it may be concluded that most degradation related to iron compounds and oxidative processes have taken place during the first period of conservation when the wood was exposed to oxygen in a still very humid state. Thus, the current rate of oxidative degradation under the present relatively dry museum conditions should be relatively low.

Molecular Weight and Tacticity of Oligoacrylates by Capillary Electrophoresis - Mass Spectrometry

2010 ◽  
Vol 63 (8) ◽  
pp. 1219 ◽  
Author(s):  
Marianne Gaborieau ◽  
Tim J. Causon ◽  
Yohann Guillaneuf ◽  
Emily F. Hilder ◽  
Patrice Castignolles
Keyword(s):  
Capillary Electrophoresis ◽  
Raft Polymerization ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Separation Mechanism ◽  
Ionization Mass ◽  
Polymeric Particles ◽  
Reversible Addition ◽  
Exclusion Chromatography

Oligo(acrylic acid) efficiently stabilizes polymeric particles, especially particles produced by reversible addition–fragmentation chain transfer (RAFT) (as hydrophilic block of an amphiphilic copolymer). Capillary electrophoresis (CE) has a far higher resolution power to separate these oligomers than the commonly used size exclusion chromatography. Coupling CE to electrospray ionization mass spectrometric detection unravels the separation mechanism. CE separates these oligomers, not only according to their degree of polymerization, but also according to their tacticity, in agreement with NMR analysis. Such analysis will provide insight into the role of these oligomers as stabilizers in emulsion polymerization, and into the mechanism of the RAFT polymerization with respect to degree of polymerization and tacticity.

scholarly journals Characterization of fractionated lignins polymerized by fungal laccases

BioResources ◽  
2011 ◽  
Vol 6 (2) ◽  
pp. 1105-1121 ◽  
Author(s):  
Daniel van de Pas ◽  
Aynsley Hickson ◽  
Lloyd Donaldson ◽  
Gareth Lloyd-Jones ◽  
Tarja Tamminen ◽  
...  
Keyword(s):  
Value Added ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Enzyme Treatment ◽  
Chemical Fractionation ◽  
Trametes Hirsuta ◽  
Melanocarpus Albomyces ◽  
Exclusion Chromatography ◽  
Optimum Reaction

Lignins are important biopolymers that can be converted into value-added materials by enzymatic treatments. However, the heterogeneity of the lignin polymer makes it a challenging material to modify. Thus, chemical fractionation was used to obtain lignins with high homogeneity in order to assess their biotechnological utilization. Commercial Alcell, birch organosolv lignins, and steam-exploded pine and eucalypt lignins were sequentially fractionated by ether, ether/acetone 4:1 (v:v), and acetone. All fractions were structurally characterized prior to treatments with Thielavia arenaria, Trametes hirsuta, and Melanocarpus albomyces laccases. The reactivities of the enzymes towards the lignins were determined by oxygen consumption measurements, and the degree of polymerization was confirmed by size exclusion chromatography. Field emission scanning electron microscopy revealed that the surfaces of the lignin nanoparticles were dispersed in the enzyme treatment, suggesting an increase in hydrophilicity of the surfaces detected as loosened morphology. Hence, it was concluded that enzyme-aided valorization is an attractive means for lignin modification, provided that optimum reaction conditions are employed.

scholarly journals CHARACTERIZATION OF INULIN FROM BLACK SALSIFY (SCORZONERA HISPANICA L.) FOR FOOD AND PHARMACEUTICAL PURPOSES

2018 ◽  
Vol 11 (12) ◽  
pp. 221 ◽  
Author(s):  
Nadezhda Petkova
Keyword(s):  
High Performance ◽  
Chemical Characterization ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Future Application ◽  
Coating Agent ◽  
Swelling Capacity ◽  
Exclusion Chromatography ◽  
Water Holding

Objective: The aim of the current study was to evaluate the black salsify (Scorzonera hispanica L.) as a potential source of inulin and to characterize the physicochemical properties of isolated polysaccharide.Methods: The carbohydrate content in its roots and leaves was analyzed by high-performance liquid chromatography with refractive index detection (HPLC-RID) method. Microwave-assisted extraction was performed for isolation of inulin from black salsify roots. The obtained polysaccharide was characterized by HPLC-RID method, HPLC size-exclusion chromatography, and Fourier transformed-infrared spectroscopy. Functional properties as swelling capacity, solubility, and water-holding and oil-holding capacities (OHCs) were also evaluated.Results: Black salsify (S. hispanica L.) roots were evaluated as a rich source of inulin (22% dw) and 1-kestose (6.25 g/100 g dw). The isolated inulin (yield 20%) was characterized with average degree of polymerization 17, with polydispersity index (1.04) that was near to medium-chained inulin. This polysaccharide showed better OHC than water-holding capacity, and it was characterized with swelling capacity 0.5 ml/g sample.Conclusion: For the first time, inulin was isolated from black salsify roots. The chemical characterization of inulin reveals the potential of this plant to be used as a valuable source of this polysaccharide for future application in food technology and pharmaceutical industry for dietary fibers, stabilizer, and coating agent.

scholarly journals The interaction of the mitochondrial protein importer TOMM34 with HSP70 is regulated by TOMM34 phosphorylation and binding to 14-3-3 adaptors

2020 ◽  
Vol 295 (27) ◽  
pp. 8928-8944 ◽  
Author(s):  
Filip Trcka ◽  
Michal Durech ◽  
Pavla Vankova ◽  
Veronika Vandova ◽  
Oliver Simoncik ◽  
...  
Keyword(s):  
Structural Changes ◽  
Protein Transport ◽  
Mitochondrial Protein ◽  
Inhibitory Effect ◽  
Size Exclusion ◽  
Tetratricopeptide Repeat ◽  
Interaction Interface ◽  
Exclusion Chromatography ◽  
Hydrogen Deuterium

Translocase of outer mitochondrial membrane 34 (TOMM34) orchestrates heat shock protein 70 (HSP70)/HSP90–mediated transport of mitochondrial precursor proteins. Here, using in vitro phosphorylation and refolding assays, analytical size-exclusion chromatography, and hydrogen/deuterium exchange MS, we found that TOMM34 associates with 14-3-3 proteins after its phosphorylation by protein kinase A (PKA). PKA preferentially targeted two serine residues in TOMM34: Ser93 and Ser160, located in the tetratricopeptide repeat 1 (TPR1) domain and the interdomain linker, respectively. Both of these residues were necessary for efficient 14-3-3 protein binding. We determined that phosphorylation-induced structural changes in TOMM34 are further augmented by binding to 14-3-3, leading to destabilization of TOMM34's secondary structure. We also observed that this interaction with 14-3-3 occludes the TOMM34 interaction interface with ATP-bound HSP70 dimers, which leaves them intact and thereby eliminates an inhibitory effect of TOMM34 on HSP70-mediated refolding in vitro. In contrast, we noted that TOMM34 in complex with 14-3-3 could bind HSP90. Both TOMM34 and 14-3-3 participated in cytosolic precursor protein transport mediated by the coordinated activities of HSP70 and HSP90. Our results provide important insights into how PKA-mediated phosphorylation and 14-3-3 binding regulate the availability of TOMM34 for its interaction with HSP70.

scholarly journals Characterization of a Novel β-Galactosidase fromBifidobacterium adolescentis DSM 20083 Active towards Transgalactooligosaccharides

2000 ◽  
Vol 66 (4) ◽  
pp. 1379-1384 ◽  
Author(s):  
Katrien M. J. Van Laere ◽  
Tjakko Abee ◽  
Henk A. Schols ◽  
Gerrit Beldman ◽  
Alphons G. J. Voragen
Keyword(s):  
Size Exclusion Chromatography ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Cell Extract ◽  
Degree Of Polymerization ◽  
Exchange Chromatography ◽  
Size Exclusion ◽  
Bifidobacterium Adolescentis ◽  
Exclusion Chromatography

ABSTRACT This paper reports on the effects of both reducing and nonreducing transgalactooligosaccharides (TOS) comprising 2 to 8 residues on the growth of Bifidobacterium adolescentis DSM 20083 and on the production of a novel β-galactosidase (β-Gal II). In cells grown on TOS, in addition to the lactose-degrading β-Gal (β-Gal I), another β-Gal (β-Gal II) was detected and it showed activity towards TOS but not towards lactose. β-Gal II activity was at least 20-fold higher when cells were grown on TOS than when cells were grown on galactose, glucose, and lactose. Subsequently, the enzyme was purified from the cell extract of TOS-grown B. adolescentis by anion-exchange chromatography, adsorption chromatography, and size-exclusion chromatography. β-Gal II has apparent molecular masses of 350 and 89 kDa as judged by size-exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively, indicating that the enzyme is active in vivo as a tetramer. β-Gal II had an optimal activity at pH 6 and was not active below pH 5. Its optimum temperature was 35°C. The enzyme showed highestV max values towards galactooligosaccharides with a low degree of polymerization. This result is in agreement with the observation that during fermentation of TOS, the di- and trisaccharides were fermented first. β-Gal II was active towards β-galactosyl residues that were 1→4, 1→6, 1→3, and 1↔1 linked, signifying its role in the metabolism of galactooligosaccharides by B. adolescentis.

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