Lignin-carbohydrate network in wood and pulps: A determinant for reactivity

Holzforschung ◽  
2007 ◽  
Vol 61 (6) ◽  
pp. 668-674 ◽  
Author(s):  
Gunnar Henriksson ◽  
Martin Lawoko ◽  
Maria Eugenia Eugenio Martin ◽  
Göran Gellerstedt
Keyword(s):  
Kraft Pulp ◽  
Structural Changes ◽  
Aqueous Sodium Hydroxide ◽  
Complete Recovery ◽  
Size Exclusion ◽  
Sodium Borate ◽  
Precipitation Process ◽  
Analytical Technique ◽  
Chemical Pulp ◽  
Exclusion Chromatography

Abstract Pretreatment of wood or kraft pulp with endoglucanase followed by swelling in urea leaves a non-crystalline residue that can be dissolved in strong aqueous sodium hydroxide-sodium borate solution. A stepwise precipitation process employing acid and barium ions can separate lignin-carbohydrate complexes enriched in individual polysaccharides. This procedure has been applied to eucalypt and birch wood and to the corresponding kraft pulps. Thioacidolysis of the various lignin-carbohydrate complexes was used as the major analytical technique to obtain information about the structure and structural changes in lignin. A combination of thioacidolysis and size exclusion chromatography was used to obtain knowledge on the degree of depolymerisation and repolymerisation of lignin when going from wood to chemical pulp. In contrast to spruce wood and kraft pulp, complete recovery of the lignin-carbohydrate complexes could not be obtained from hardwood samples.

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.

Photosensitized Delignification of Residual Lignin and Chemical Pulp from Eucalyptus grandis Wood

Holzforschung ◽  
2002 ◽  
Vol 56 (6) ◽  
pp. 595-600 ◽  
Author(s):  
D. Da Silva Perez ◽  
A. Castellan ◽  
A. Nourmamode ◽  
S. Grelier ◽  
R. Ruggiero ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Methylene Blue ◽  
Eucalyptus Grandis ◽  
Photochemical Reactions ◽  
Size Exclusion ◽  
Residual Lignin ◽  
Bleaching Process ◽  
Chemical Pulp ◽  
Exclusion Chromatography ◽  
Unbleached Pulp

Summary Bleached pulps were obtained from a Eucalyptus grandis peroxyformic/formic acid chemical pulp using oxygen, hydrogen peroxide, photosensitizers (methylene blue, Fe (II) 4,4′,4″,4‴-tetrasulfophthalocyanine, hemin, hematoporphyrin) and/or TiO2. Residual lignin of unbleached pulp, isolated and characterized by size exclusion chromatography, 31P NMR and thioacidolysis, was used to study the photochemical reactions occurring during the bleaching process. The main reactions were conversion of phenolic aromatic units into carboxylic acids and cleavage of the β-O-4 ether bonds leading to a depolymerization of the lignin framework into smaller fragments.

Size exclusion chromatographic and UV-VIS absorption analyses of unbleached and bleached softwood kraft pulps using LiCl/1,3-dimethyl-2-imidazolidinone as a solvent

Holzforschung ◽  
2007 ◽  
Vol 61 (3) ◽  
pp. 236-241 ◽  
Author(s):  
Masahiro Yanagisawa ◽  
Akira Isogai
Keyword(s):  
Kraft Pulp ◽  
Total Yield ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Light Scattering Detection ◽  
Exclusion Chromatography ◽  
Photodiode Array ◽  
Sulfite Pulp

Abstract Unbleached and bleached kraft pulps and holocellulose prepared from softwood were totally soluble in 8% LiCl/1,3-dimethyl-2-imidazolidinone (LiCl/DMI). The solutions were analyzed by size exclusion chromatography with photodiode array and multi-angle laser light scattering detection (SEC-PDA-MALLS). The mobile phase consisted of 1% LiCl/DMI. The degree of polymerization (DP) and DP distribution of the softwood kraft pulps were determined, as well as the DP distribution of residual lignins based on their UV-VIS absorption patterns. Changes in DP for kraft pulps after a conventional bleaching sequence were evaluated, and the residual lignins were analyzed in the same way. Approximately half of the residual lignin in unbleached and bleached kraft pulps was present in polysaccharide fractions with high DP, which represented approximately 90% of the total yield. Some characteristic differences in the UV-VIS absorption pattern were observed between kraft pulps bleached with oxygen and chlorine. DP, DP distribution of polysaccharides, and distribution of residual lignin were clearly different for unbleached kraft pulp, unbleached sulfite pulp, and holocellulose. An unbleached kraft pulp prepared from hardwood showed different properties to the corresponding softwood preparation. The UV-VIS absorption patterns due to residual lignins were also very characteristic for the various pulps and holocellulose.

scholarly journals Structural Features and Rheological Properties of a Sulfated Xylogalactan-Rich Fraction Isolated from Tunisian Red Seaweed Jania adhaerens

2020 ◽  
Vol 10 (5) ◽  
pp. 1655 ◽  
Author(s):  
Faiez Hentati ◽  
Cédric Delattre ◽  
Christine Gardarin ◽  
Jacques Desbrières ◽  
Didier Le Cerf ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Flow Characteristics ◽  
Structural Features ◽  
Sulfated Polysaccharide ◽  
Size Exclusion ◽  
Random Coil ◽  
Precipitation Process ◽  
Resonance Spectroscopy ◽  
Exclusion Chromatography ◽  
Average Molecular Masses

A novel sulfated xylogalactan-rich fraction (JSP for J. adhaerens Sulfated Polysaccharide) was extracted from the red Tunisian seaweed Jania adhaerens. JSP was purified using an alcoholic precipitation process and characterized by Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR), high-pressure size exclusion chromatography (HPSEC) with a multi-angle laser light scattering (MALLS), gas chromatography coupled to mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR, 1D and 2D). JSP was then evaluated regarding its physicochemical and rheological properties. Results showed that JSP was mainly composed of an agar-like xylogalactan sharing the general characteristics of corallinans. The structure of JSP was mainly composed of agaran disaccharidic repeating units (→3)-β-d-Galp-(1,4)-α-l-Galp-(1→)n and (→3)-β-d-Galp-(1,4)-3,6-α-l-AnGalp-(1→)n, mainly substituted on O-6 of (1,3)-β-d-Galp residues by β-xylosyl side chains, and less with sulfate or methoxy groups. (1,4)-α-l-Galp residues were also substituted by methoxy and/or sulfate groups in the O-2 and O-3 positions. Mass-average and number-average molecular masses (Mw) and (Mn), intrinsic viscosity ([η]) and hydrodynamic radius (Rh) for JSP were, respectively, 8.0 × 105 g/mol, 1.0 × 105 g/mol, 76 mL/g and 16.8 nm, showing a flexible random coil conformation in solution. The critical overlap concentration C* of JSP was evaluated at 7.5 g/L using the Williamson model. In the semi-diluted regime, JSP solutions displayed a shear-thinning behavior with a great viscoelasticity character influenced by temperature and monovalent salts. The flow characteristics of JSP were described by the Ostwald model.

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.

scholarly journals Understanding the structural changes of lignin in poplar following steam explosion pretreatment

Holzforschung ◽  
2020 ◽  
Vol 74 (3) ◽  
pp. 275-285 ◽  
Author(s):  
Huimei Wang ◽  
Zhong Liu ◽  
Lanfeng Hui ◽  
Lan Ma ◽  
Xu Zheng ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Magnetic Resonance ◽  
Steam Explosion ◽  
Quantum Coherence ◽  
Structural Changes ◽  
Average Molecular Weight ◽  
Size Exclusion ◽  
Single Quantum ◽  
Exclusion Chromatography ◽  
G Ratio

AbstractTo understand the modifications of lignin in the steam explosion process (209°C, 7 min), lignin samples in native poplar (LP), steam explosion solid residue (LS) and steam explosion liquid (LL) were separated and studied. The lignin samples (LP, LS and LL) were characterized and analyzed by size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance [carbon 13 numclear magnetic resonance (13C-NMR) and heteronuclear single quantum coherence or heteronuclear single quantum correlation experiment NMR (HSQC) NMR] analysis. The results revealed that the pretreatment induced reductions in amounts of β-O-4′, β-β′, and spirodienone structure, and increases in the syringyl/guaiacyl (S/G) ratio from 1.14 (LP) to 1.70 (LS) and 1.86 (LL). The HSQC NMR spectra also gave more information about the predominance of G and S units, and only small amounts of p-hydroxyphenyl (H) units. Moreover, SEC demonstrated the depolymerization and repolymerization of lignin, which were the main reasons for the increase in the average molecular weight of LS and the decrease in average molecular weight of LL, respectively. In brief, after steam explosion treatment, the lignin structure changed, but the backbone structure was not noticeably modified.

scholarly journals Variable-Temperature Size Exclusion Chromatography for the Study of the Structural Changes in G-Quadruplex

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Sanae Benabou ◽  
Ramon Eritja ◽  
Raimundo Gargallo
Keyword(s):  
Size Exclusion Chromatography ◽  
Promoter Region ◽  
Structural Changes ◽  
Variable Temperature ◽  
Size Exclusion ◽  
G Quadruplex ◽  
Conformational Equilibria ◽  
Exclusion Chromatography ◽  
In The Wild ◽  
Circular Dichroïsm

The conformational equilibria of a guanine-rich sequence found at the promoter region of the human c-kit oncogene are studied by means of circular dichroism spectroscopy (CD) and variable-temperature size exclusion chromatography (SEC). It is shown that the wild sequence ckit21 exists as a mixture of monomeric and multimeric G-quadruplexes. Appropriate mutation of several bases in the wild sequence produces the shift from parallel to antiparallel G-quadruplex, as well as the disappearance of multimeric species. The shift from the antiparallel to the parallel conformation induced by temperature is reflected in both CD and SEC profiles.

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