scholarly journals Contribution of xylan to the brightness development and stability in the final ECF bleaching of eucalypt (Eucalyptus globulus Labill.) kraft pulp

Holzforschung ◽  
2013 ◽  
Vol 67 (5) ◽  
pp. 497-503 ◽  
Author(s):  
Pedro E.G. Loureiro ◽  
Joana I.T. Sousa ◽  
M. Graça. V.S. Carvalho ◽  
Dmitry V. Evtuguin
Keyword(s):  
Analytical Methods ◽  
Kraft Pulp ◽  
Resonance Raman Spectroscopy ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Vis Spectroscopy ◽  
Exclusion Chromatography ◽  
Uv Resonance Raman Spectroscopy ◽  
Modern Analytical

Abstract Xylans isolated from eucalypt kraft pulps have been characterized by modern analytical methods. The pulps were partially bleached (DEOPD) and fully bleached with either a final ClO2 (DEOPDD) or an alkaline H2O2 (DEOPDP) bleaching stage. Alternatively, xylan isolated from the DEOPD pulp was treated with ClO2 or with H2O2 under the same conditions as pulps in a final bleaching stage and were further characterized. 1H nuclear magnetic resonance, size exclusion chromatography, UV-vis spectroscopy in cadoxen solution, and UV-resonance Raman spectroscopy were applied as analytical methods. The final ClO2 stage generated new unsaturated moieties in xylan, whereas H2O2 was very effective in the removal of xylan-related chromophores. The role of xylan to the delay of brightness development in the final ClO2 stage was highlighted by means of a pretreatment with xylanase Pulpzyme HC before the final bleaching stage. By this approach, the final bleachability of the pulp was boosted and the brightness stability of the fully bleached pulp was improved.

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.

Study on Alkali-Accessible Chromophores from Unbleached Kraft Pulp

Holzforschung ◽  
2001 ◽  
Vol 55 (5) ◽  
pp. 554-558 ◽  
Author(s):  
T. Bikova ◽  
V. Klevinska ◽  
T. Eremeeva ◽  
A. Treimanis
Keyword(s):  
Kraft Pulp ◽  
Kraft Lignin ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Black Alder ◽  
Alkaline Extract ◽  
Alkali Solutions ◽  
Exclusion Chromatography ◽  
Soluble Lignin ◽  
Cooking Conditions

Summary An approach to a chromophore composition study using the direct size-exclusion chromatography (SEC-UV) analysis of an alkaline extract of pulp fibre walls is described. Absorbance in the 290–405 nm range of 2% and 18% NaOH extract from unbleached pulps obtained by conventional and extended kraft delignification of black alder wood is compared. The effect of cooking conditions on the localisation and accessibility of chromophores is elucidated. The alkali-soluble lignin from pulp produced by extended cooking was less oxidised, less conjugated, and less coloured as compared with the conventional kraft lignin. A chromophore accessibility index is proposed. The chromogenic structures in pulps obtained by extended cooking were more resistant to alkali solutions than those in conventional kraft pulps.

scholarly journals Metagenomic Profiling of Fecal-Derived Bacterial Membrane Vesicles in Crohn’s Disease Patients

Cells ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2795
Author(s):  
Nader Kameli ◽  
Heike E. F. Becker ◽  
Tessa Welbers ◽  
Daisy M. A. E. Jonkers ◽  
John Penders ◽  
...  
Keyword(s):  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Membrane Vesicles ◽  
Amplicon Sequencing ◽  
Size Exclusion ◽  
Bacterial Membrane ◽  
Microbial Composition ◽  
Fecal Samples ◽  
Exclusion Chromatography

Background: In the past, many studies suggested a crucial role for dysbiosis of the gut microbiota in the etiology of Crohn’s disease (CD). However, despite being important players in host–bacteria interaction, the role of bacterial membrane vesicles (MV) has been largely overlooked in the pathogenesis of CD. In this study, we addressed the composition of the bacterial and MV composition in fecal samples of CD patients and compared this to the composition in healthy individuals. Methods: Fecal samples from six healthy subjects (HC) in addition to twelve CD patients (six active, six remission) were analyzed in this study. Fecal bacterial membrane vesicles (fMVs) were isolated by a combination of ultrafiltration and size exclusion chromatography. DNA was obtained from the fMV fraction, the pellet of dissolved feces as bacterial DNA (bDNA), or directly from feces as fecal DNA (fDNA). The fMVs were characterized by nanoparticle tracking analysis and cryo-electron microscopy. Amplicon sequencing of 16s rRNA V4 hypervariable gene regions was conducted to assess microbial composition of all fractions. Results: Beta-diversity analysis showed that the microbial community structure of the fMVs was significantly different from the microbial profiles of the fDNA and bDNA. However, no differences were observed in microbial composition between fDNA and bDNA. The microbial richness of fMVs was significantly decreased in CD patients compared to HC, and even lower in active patients. Profiling of fDNA and bDNA demonstrated that Firmicutes was the most dominant phylum in these fractions, while in fMVs Bacteroidetes was dominant. In fMV, several families and genera belonging to Firmicutes and Proteobacteria were significantly altered in CD patients when compared to HC. Conclusion: The microbial alterations of MVs in CD patients particularly in Firmicutes and Proteobacteria suggest a possible role of MVs in host-microbe symbiosis and induction or progression of inflammation in CD pathogenesis. Yet, the exact role for these fMV in the pathogenesis of the disease needs to be elucidated in future studies.

scholarly journals Synthesis of L-DOPA Based Melanins with Reproducible Physic-Chemical Properties

2018 ◽  
Author(s):  
Koen Vercruysse ◽  
Jayla Moore
Keyword(s):  
Ir Spectroscopy ◽  
Enzymatic Synthesis ◽  
Chemical Properties ◽  
Size Exclusion ◽  
Synthesis Methods ◽  
Ongoing Research ◽  
Vis Spectroscopy ◽  
Exclusion Chromatography ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

This report expands our ongoing research efforts into the non-enzymatic synthesis of melanins. We have explored four different methods for the synthesis of L-DOPA based melanins and evaluated the reproducibility of some of their physic-chemical properties. The melanins were synthesized through the addition of NaOH, tyrosinate or Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub>. Two different approaches for the reactions involving Fe<sup>2+</sup> and H<sub>2</sub>O<sub>2</sub> were tested: a) addition of H<sub>2</sub>O<sub>2</sub> spread out over multiple days or b) addition of H<sub>2</sub>O<sub>2</sub> in one fraction at the start of the reaction. The physic-chemical properties of the melanins explored involved: 1) retention on size exclusion chromatography column, 2) FT-IR spectroscopy, 3) UV-Vis spectroscopy and 4) the capacity to reduce a redox dye, dichlorophenolindophenol. Overall the results obtained indicated that 1) the various synthesis methods lead to melanins with reproducible physic-chemical properties, 2) that the melanins synthesized in the presence of Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub> are distinctly different from the melanins synthesized in the presence of NaOH or tyrosinate and 3) that no distinctly different melanins were generated when comparing the two different synthesis approaches involving Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub>. Only the melanins synthesized in the presence of Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub> appeared to possess the capacity to reduce dichlorophenolindophenol.

scholarly journals The Two ADF-H Domains of Twinfilin Play Functionally Distinct Roles in Interactions with Actin Monomers

2002 ◽  
Vol 13 (11) ◽  
pp. 3811-3821 ◽  
Author(s):  
Pauli J. Ojala ◽  
Ville O. Paavilainen ◽  
Maria K. Vartiainen ◽  
Roman Tuma ◽  
Alan G. Weeds ◽  
...  
Keyword(s):  
Binding Site ◽  
Binding Activity ◽  
Size Exclusion ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Monomer ◽  
Wild Type ◽  
Native Page ◽  
Exclusion Chromatography

Twinfilin is a ubiquitous and abundant actin monomer–binding protein that is composed of two ADF-H domains. To elucidate the role of twinfilin in actin dynamics, we examined the interactions of mouse twinfilin and its isolated ADF-H domains with G-actin. Wild-type twinfilin binds ADP-G-actin with higher affinity (K D = 0.05 μM) than ATP-G-actin (K D = 0.47 μM) under physiological ionic conditions and forms a relatively stable (k off = 1.8 s−1) complex with ADP-G-actin. Data from native PAGE and size exclusion chromatography coupled with light scattering suggest that twinfilin competes with ADF/cofilin for the high-affinity binding site on actin monomers, although at higher concentrations, twinfilin, cofilin, and actin may also form a ternary complex. By systematic deletion analysis, we show that the actin-binding activity is located entirely in the two ADF-H domains of twinfilin. Individually, these domains compete for the same binding site on actin, but the C-terminal ADF-H domain, which has >10-fold higher affinity for ADP-G-actin, is almost entirely responsible for the ability of twinfilin to increase the amount of monomeric actin in cosedimentation assays. Isolated ADF-H domains associate with ADP-G-actin with rapid second-order kinetics, whereas the association of wild-type twinfilin with G-actin exhibits kinetics consistent with a two-step binding process. These data suggest that the association with an actin monomer induces a first-order conformational change within the twinfilin molecule. On the basis of these results, we propose a kinetic model for the role of twinfilin in actin dynamics and its possible function in cells.

Reactions of aromatic structures in brightness reversion of fully-bleached eucalyptus kraft pulps

Holzforschung ◽  
2009 ◽  
Vol 63 (3) ◽  
Author(s):  
Anna-Stiina Jääskeläinen ◽  
Katri Toikka ◽  
Anni Lähdetie ◽  
Tiina Liitiä ◽  
Tapani Vuorinen
Keyword(s):  
Resonance Raman ◽  
Kraft Pulps ◽  
Brightness Reversion ◽  
Vis Spectroscopy ◽  
Uv Resonance Raman ◽  
Hexenuronic Acid

Abstract The role of aromatic structures in brightness reversion of fully bleached pulps was studied by UV resonance Raman (UVRR) and reflectance UV-Vis spectroscopy. The results clearly showed that ageing increased the aromatic band at approximately 1600 cm-1 in the UVRR spectra and the lignin band at approximately 280 nm in the UV-Vis spectra. This increase was probably due to increased conjugation of lignin and it was observed for all pulps regardless of the bleaching sequence. In addition to these lignin reactions, other unsaturated structures, such as hexenuronic acid groups, reacted during ageing.

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.

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