The chemical composition of the lipids in wheat straw was studied in detail by gas chromatography and mass spectrometry. Important discrepancies with the data reported in previous papers were found. ...The predominant lipids identified were series of long-chain free fatty acids (25% of total extract), followed by series of free fatty alcohols (ca. 20%). High molecular weight esters of long chain fatty acids esterified to long chain fatty alcohols were also found (11%), together with lower amounts of other aliphatic series, such as n-alkanes, n-aldehydes, and glycerides (mono-, di-, and triglycerides). Relatively high amounts of β-diketones (10%), particularly 14,16-hentriacontanedione, which is the second most abundant single compound among the lipids in wheat straw, were also identified. Finally, steroid compounds (steroid hydrocarbons, steroid ketones, free sterols, sterol esters, and sterol glycosides) were also found, with sterols accounting for nearly 14% of all identified compounds.
The recent development of prime editing (PE) genome engineering technologies has the potential to significantly simplify the generation of human pluripotent stem cell (hPSC)-based disease models. PE ...is a multicomponent editing system that uses a Cas9-nickase fused to a reverse transcriptase (nCas9-RT) and an extended PE guide RNA (pegRNA). Once reverse transcribed, the pegRNA extension functions as a repair template to introduce precise designer mutations at the target site. Here, we systematically compared the editing efficiencies of PE to conventional gene editing methods in hPSCs. This analysis revealed that PE is overall more efficient and precise than homology-directed repair of site-specific nuclease-induced double-strand breaks. Specifically, PE is more effective in generating heterozygous editing events to create autosomal dominant disease-associated mutations. By stably integrating the nCas9-RT into hPSCs we achieved editing efficiencies equal to those reported for cancer cells, suggesting that the expression of the PE components, rather than cell-intrinsic features, limit PE in hPSCs. To improve the efficiency of PE in hPSCs, we optimized the delivery modalities for the PE components. Delivery of the nCas9-RT as mRNA combined with synthetically generated, chemically-modified pegRNAs and nicking guide RNAs improved editing efficiencies up to 13-fold compared with transfecting the PE components as plasmids or ribonucleoprotein particles. Finally, we demonstrated that this mRNA-based delivery approach can be used repeatedly to yield editing efficiencies exceeding 60% and to correct or introduce familial mutations causing Parkinson's disease in hPSCs.
▸ A laccase-mediator treatment removed lignin from whole woody and nonwoody feedstocks. ▸ A high-redox potential laccase and 1-hydroxybenzotriazole (as mediator) were used. ▸ This laccase-mediator ...treatment was combined with an alkaline peroxide extraction. ▸ 2D NMR analyses revealed oxidative removal of lignin aromatic units and side-chains. ▸ The enzymatic pretreatment increased the sugar and ethanol yields.
The ability of Trametes villosa laccase, in conjuction with 1-hydroxybenzotriazole (HBT) as mediator and alkaline extraction, to remove lignin was demonstrated during treatment of wood (Eucalyptus globulus) and non-wood (Pennisetum purpureum) feedstocks. At 50Ug−1 laccase and 2.5% HBT concentration, 48% and 32% of the Eucalyptus and Pennisetum lignin were removed, respectively. Two-dimensional nuclear magnetic resonance of the feedstocks, swollen in dimethylsulfoxide-d6, revealed the removal of p-hydroxyphenyl, guaiacyl and syringyl lignin units and aliphatic (mainly β-O-4′-linked) side-chains of lignin, and a moderate removal of p-coumaric acid (present in Pennisetum) without a substantial change in polysaccharide cross-signals. The enzymatic pretreatment (at 25Ug−1) of Eucalyptus and Pennisetum feedstocks increased the glucose (by 61% and 12% in 72h) and ethanol (by 4 and 2gL−1 in 17h) yields from both lignocellulosic materials, respectively, as compared to those without enzyme treatment.
Three plant phenols, namely acetosyringone, syringaldehyde and
p-coumaric acid, were selected as laccase redox mediators to investigate the enzymatic delignification of paper pulp (obtained from ...kraft cooking of eucalypt wood) in combination with peroxide bleaching. The effects of these natural mediators were compared with those obtained using the synthetic mediator 1-hydroxybenzotriazole.
p-Coumaric acid only caused minor increase of pulp brightness and did not lower its kappa number (a rough estimation of the lignin content), whereas, the use of acetosyringone or syringaldehyde as laccase mediators enabled over 15% increase of final brightness and a similar decrease of final kappa number. Pulp delignification by laccase in the presence of the two latter natural mediators was demonstrated by analytical pyrolysis, which does not suffer from interferences by other pulp constituents as kappa number does, showing a preferential removal of lignin marker compounds compared with carbohydrate markers (up to 25% decrease of the corresponding ratio). This technique also revealed a modification of the residual lignin composition in terms of phenylpropane units after the laccase-mediator treatment. The use of laccase in combination with natural mediators, widely available from plant materials and pulping liquors, represents a promising alternative for environmentally friendly delignification of paper pulp.
For individuals with human immunodeficiency virus (HIV) infection to fully benefit from potent combination antiretroviral therapy, they need to know that they are HIV infected, be engaged in regular ...HIV care, and receive and adhere to effective antiretroviral therapy. Test-and-treat strategies for HIV prevention posit that expanded testing and earlier treatment of HIV infection could markedly decrease ongoing HIV transmission, stemming the HIV epidemic. However, poor engagement in care for HIV-infected individuals will substantially limit the effectiveness of test-and-treat strategies. We review the spectrum of engagement in care for HIV-infected individuals in the United States and apply this information to help understand the magnitude of the challenges that poor engagement in care will pose to test-and-treat strategies for HIV prevention.
Although alternative pre-mRNA splicing (AS) significantly diversifies the neuronal proteome, the extent of AS is still unknown due in part to the large number of diverse cell types in the brain. To ...address this complexity issue, we used an annotation-free computational method to analyze and compare the AS profiles between small specific groups of
circadian neurons. The method, the Junction Usage Model (JUM), allows the comprehensive profiling of both known and novel AS events from specific RNA-seq libraries. The results show that many diverse and novel pre-mRNA isoforms are preferentially expressed in one class of clock neuron and also absent from the more standard
head RNA preparation. These AS events are enriched in potassium channels important for neuronal firing, and there are also cycling isoforms with no detectable underlying transcriptional oscillations. The results suggest massive AS regulation in the brain that is also likely important for circadian regulation.
Summary
Selective modification/degradation of the main plant polymers (cellulose, hemicelluloses and lignin) was investigated in a hardwood after white and brown‐rot fungal decay under environmental ...conditions. The chemical changes produced in the plant cell wall were analysed in situ, by nuclear magnetic resonance (NMR) at the gel state, and analytical pyrolysis. Two‐dimensional (2D) NMR of the white‐rotted wood showed only cellulose and (deacetylated) hemicellulose, and the complete removal of lignin. On the other hand, the brown‐rotted wood showed the nearly complete absence of polysaccharides, while the main features of lignin structure, as revealed by 2D‐NMR, could be observed. These included well‐resolved aromatic and side‐chain cross‐signals, although the intensity of the latter signals was lowered indicating a reduction in the number of side‐chain linkages (β‐O‐4′ and β‐β′) per aromatic unit (their relative abundances remaining unchanged). These results contrast with a recent study concluding that the aromatic polymer after brown‐rot decay is not longer recognized as lignin. Some oxidative alteration of lignin during brown‐rot decay was evidenced and, more interesting, several compounds with 3‐methoxycatechol skeleton were released upon pyrolysis. Lignin demethylation is consistent with recent brown‐rot transcriptomic/secretomic studies showing overexpression of methanol oxidase, which could use lignin‐derived methanol to generate the peroxide required for cellulose depolymerization via Fenton chemistry.
Occurrence of Naturally Acetylated Lignin Units Del Río, José C; Marques, Gisela; Rencoret, Jorge ...
Journal of agricultural and food chemistry,
07/2007, Letnik:
55, Številka:
14
Journal Article
Recenzirano
Odprti dostop
This work examines the occurrence of native acetylated lignin in a large set of vascular plants, including both angiosperms and gymnosperms, by a modification of the so-called Derivatization Followed ...by Reductive Cleavage (DFRC) method. Acetylated lignin units were found in the milled wood lignins of all angiosperms selected for this study, including mono- and eudicotyledons, but were absent in the gymnosperms analyzed. In some plants (e.g., abaca, sisal, kenaf, or hornbeam), lignin acetylation occurred at a very high extent, exceeding 45% of the uncondensed (alkyl-aryl ether linked) syringyl lignin units. Acetylation was observed exclusively at the γ-carbon of the lignin side chain and predominantly on syringyl units, although a predominance of acetylated guaiacyl over syringyl units was observed in some plants. In all cases, acetylation appears to occur at the monomer stage, and sinapyl and coniferyl acetates seem to behave as real lignin monomers participating in lignification. Keywords: Lignin; angiosperms; gymnosperms; eudicotyledons; monocotyledons; coniferyl acetate; sinapyl acetate; abaca; sisal; kenaf; hornbeam; Derivatization Followed by Reductive Cleavage (DFRC)
This work describes the preparation of hybrid membranes using octaphenyl polyhedral oligomeric silsesquioxane Ph sub(8)Si sub(8)O sub(12) (POSS), either partially sulfonated (30%) or non-sulfonated ...as a filler and Nafion as polymer matrix. The membranes have been evaluated in terms of thermal stability (TGA, DSC), water uptake and ex situ in-plane proton conductivity. Morphology has been investigated using SEM and AFM. The hybrid membranes were electrochemically characterized into single cells in order to determine in situ through-plane proton conductivity, hydrogen crossover and cell performance. The analysis was made at 80 degree C cell temperature, atmospheric pressure and different levels of relative humidity. The results showed the potential applicability of these membrane materials as electrolytes in PEMFC at medium/low humidity conditions.
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