| 1. |
- Feng, Nianjie, et al.
(författare)
-
Changes in chemical structures of wheat straw auto-hydrolysis lignin by 3-hydroxyanthranilic acid as a laccase mediator
- 2019
-
Ingår i: International Journal of Biological Macromolecules. - : ELSEVIER SCIENCE BV. - 0141-8130 .- 1879-0003. ; 122, s. 210-215
-
Tidskriftsartikel (refereegranskat)abstract
- 3-Hydroxyanthranilic acid (3-HAA), as a potential natural laccase mediator, was shown to mediate the oxidation of non-phenolic lignin subunits. The problem of cost and toxicity of artificial mediators could be solved to some extent by a further study about the detailed changes of lignin chemistry structures in laccase 3-HAA system (LHS). In this work, wheat straw auto-hydrolysis lignin (AL) was prepared. Oxidations of AL by LHS and laccase 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) system were then investigated, respectively. Various structural changes of AL during the oxidation were characterized by different methods including phenolic hydroxyl group determination, nitrobenzene oxidation, ozonation, gel permeation chromatography, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy. The changes in AL chemical structures were found in LHS, including unit removal, bond cleavage and biopolymerization. Compared to laccase ABTS system, a selective removal of guaiacyl-type lignin in LHS was observed, based on the results of nitrobenzene oxidation and 2D NMR analysis. The selective removal of guaiacyl-type lignin was due to improved aromatic ring cleavage and weaken lignin biopolymerization. The selectivity of guaiacyl-type lignin removal in LHS plays an important role, especially for improving bioconversion efficiency of laccase for guaiacyl-rich lignocellulosic biomass.
|
|
| 2. |
- Guo, Lifang, et al.
(författare)
-
Improving the compatibility, surface strength, and dimensional stability of cellulosic fibers using glycidyl methacrylate grafting
- 2020
-
Ingår i: Journal of Materials Science. - : Springer. - 0022-2461 .- 1573-4803. ; 55:27, s. 12906-12920
-
Tidskriftsartikel (refereegranskat)abstract
- The graft copolymerization of lignocellulosic fibers with glycidyl methacrylate (GMA) using a Fe2+-thiourea dioxide-H(2)O(2)redox system (Fe2+-TD-H2O2) was studied to overcome the problems of poor compatibility and low surface strength when cellulosic fibers are composited with synthetic polymers. The results show that cellulose-poly(GMA) (CPGMA) was successfully synthesized from GMA and bleachedEucalyptuscellulosic fibers by Fe2+-TD-H(2)O(2)in a mild aqueous solution. CPGMA had high graft rate (244%), high content of epoxy group, and high stability in water. X-ray diffraction patterns and(13)C cross-polarization magic angle spinning nuclear magnetic resonance spectra analyses showed that graft copolymerization did not change the crystalline structure of the CPGMA fiber backbone cellulose, but the crystallinity of the CPGMA fiber decreased with an increase in amorphous PGMA grafting. Scanning electron microscopy confirmed that the grafting reaction occurred both inside and outside the fiber. The specific surface area and pore diameter of the grafted fibers were significantly affected by the grafting. The hydrophobicity of the fibers was significantly enhanced by graft copolymerization. PGMA grafting can enhance the compatibility between the modified fiber and synthetic polymer matrix, improving the processing runnability and product properties of composite materials. A high intensity focused ultrasound method was used to analyze the fiber surface strength. It was confirmed that graft copolymerization significantly improved the surface strength of the grafted fibers. Graft copolymerization can significantly improve the dimensional stability of cellulosic fibers.
|
|
| 3. |
- Guo, Lifang, et al.
(författare)
-
Structural and functional modification of cellulose nanofibrils using graft copolymerization with glycidyl methacrylate by Fe 2+ –thiourea dioxide–H 2 O 2 redox system
- 2019
-
Ingår i: Cellulose. - : Springer Netherlands. - 0969-0239 .- 1572-882X. ; 26:8, s. 4853-4864
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract: To graft epoxy and ester functional groups onto cellulose nanofibrils (CNFs) and to overcome their poor hydrophobicity, we studied the modification of CNFs using graft copolymerization with glycidyl methacrylate (GMA) by a Fe 2+ –thiourea dioxide–H 2 O 2 initiator system (Fe 2+ –TD–H 2 O 2 ) in aqueous solution. The synthesized poly (GMA)-grafted CNF (CNF-g-PGMA) was characterized by FTIR, AFM, XRD, water contact angle, and TGA. GMA was successfully grafted onto the CNFs by Fe 2+ –TD–H 2 O 2 , the epoxy groups and ester groups of GMA were clearly present and intact in the CNF-g-PGMA, and TD is an important component of the initiator system under relatively mild graft conditions. CNF-g-PGMA may be an important intermediate because of its epoxy and ester functional groups. The main nanostructure of the CNFs was retained after graft copolymerization, and there were no obvious effects of graft copolymerization on the crystalline structure of the CNF backbone, although the crystalline index slightly decreased with the increased percentage of grafting. Graft copolymerization significantly modifies the CNF hydrophobicity. This strategy could extend the applications of CNFs into many areas. Graphical abstract: [Figure not available: see fulltext.]
|
|
| 4. |
- Weinstock, Joshua S, et al.
(författare)
-
Aberrant activation of TCL1A promotes stem cell expansion in clonal haematopoiesis.
- 2023
-
Ingår i: Nature. - 1476-4687. ; 616:7958, s. 755-763
-
Tidskriftsartikel (refereegranskat)abstract
- Mutations in a diverse set of driver genes increase the fitness of haematopoietic stem cells (HSCs), leading to clonal haematopoiesis1. These lesions are precursors for blood cancers2-6, but the basis of their fitness advantage remains largely unknown, partly owing to a paucity of large cohorts in which the clonal expansion rate has been assessed by longitudinal sampling. Here, to circumvent this limitation, we developed a method to infer the expansion rate from data from a single time point. We applied this method to 5,071 people with clonal haematopoiesis. A genome-wide association study revealed that a common inherited polymorphism in the TCL1A promoter was associated with a slower expansion rate in clonal haematopoiesis overall, but the effect varied by driver gene. Those carrying this protective allele exhibited markedly reduced growth rates or prevalence of clones with driver mutations in TET2, ASXL1, SF3B1 and SRSF2, butthis effect was not seen inclones withdriver mutations in DNMT3A. TCL1A was not expressed in normal or DNMT3A-mutated HSCs, but the introduction of mutations in TET2 or ASXL1 led to the expression of TCL1A protein and the expansion of HSCs in vitro. The protective allele restricted TCL1A expression and expansion of mutant HSCs, as did experimentalknockdown of TCL1A expression. Forced expression of TCL1A promoted the expansion of human HSCs in vitro and mouse HSCs in vivo. Our results indicate that the fitness advantage of several commonly mutated driver genes in clonal haematopoiesis may be mediated by TCL1A activation.
|
|
