The interaction between xylan and cellulose microfibrils is important for secondary cell wall properties in vascular plants; however, the molecular arrangement of xylan in the cell wall and the ...nature of the molecular bonding between the polysaccharides are unknown. In dicots, the xylan backbone of β‐(1,4)‐linked xylosyl residues is decorated by occasional glucuronic acid, and approximately one‐half of the xylosyl residues are O‐acetylated at C‐2 or C‐3. We recently proposed that the even, periodic spacing of GlcA residues in the major domain of dicot xylan might allow the xylan backbone to fold as a twofold helical screw to facilitate alignment along, and stable interaction with, cellulose fibrils; however, such an interaction might be adversely impacted by random acetylation of the xylan backbone. Here, we investigated the arrangement of acetyl residues in Arabidopsis xylan using mass spectrometry and NMR. Alternate xylosyl residues along the backbone are acetylated. Using molecular dynamics simulation, we found that a twofold helical screw conformation of xylan is stable in interactions with both hydrophilic and hydrophobic cellulose faces. Tight docking of xylan on the hydrophilic faces is feasible only for xylan decorated on alternate residues and folded as a twofold helical screw. The findings suggest an explanation for the importance of acetylation for xylan–cellulose interactions, and also have implications for our understanding of cell wall molecular architecture and properties, and biological degradation by pathogens and fungi. They will also impact strategies to improve lignocellulose processing for biorefining and bioenergy.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The interaction between cellulose and xylan is important for the load-bearing secondary cell wall of flowering plants. Based on the precise, evenly spaced pattern of acetyl and glucuronosyl (MeGlcA) ...xylan substitutions in eudicots, we recently proposed that an unsubstituted face of xylan in a 2-fold helical screw can hydrogen bond to the hydrophilic surfaces of cellulose microfibrils. In gymnosperm cell walls, any role for xylan is unclear, and glucomannan is thought to be the important cellulose-binding polysaccharide. Here, we analyzed xylan from the secondary cell walls of the four gymnosperm lineages (Conifer, Gingko, Cycad, and Gnetophyta). Conifer, Gingko, and Cycad xylan lacks acetylation but is modified by arabinose and MeGlcA. Interestingly, the arabinosyl substitutions are located two xylosyl residues from MeGlcA, which is itself placed precisely on every sixth xylosyl residue. Notably, the Gnetophyta xylan is more akin to early-branching angiosperms and eudicot xylan, lacking arabinose but possessing acetylation on alternate xylosyl residues. All these precise substitution patterns are compatible with gymnosperm xylan binding to hydrophilic surfaces of cellulose. Molecular dynamics simulations support the stable binding of 2-fold screw conifer xylan to the hydrophilic face of cellulose microfibrils. Moreover, the binding of multiple xylan chains to adjacent planes of the cellulose fibril stabilizes the interaction further. Our results show that the type of xylan substitution varies, but an even pattern of xylan substitution is maintained among vascular plants. This suggests that 2-fold screw xylan binds hydrophilic faces of cellulose in eudicots, early-branching angiosperm, and gymnosperm cell walls.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, ...particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (T.sub.CORE) and consistently greater perceived exertion while running at 35°C (p < 0.05). These changes were associated with a slower pace, evidenced by an additional 14 ± 5 min (mean ± SD) to complete the 10 km at 35°C than at 25°C (p < 0.05). Before, immediately after, and 1 h after the self-paced run, the participants performed CMJs to evaluate lower limb neuromuscular fatigue. CMJ height was reduced by 7.0% (2.3 ± 2.4 cm) at 1 h after the race (p < 0.05) compared to pre-exercise values; environmental conditions did not influence this reduction. In conclusion, despite the reduced endurance performance, higher perceived exertion, and transiently augmented T.sub.CORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this work, the application of ozone-driven processes for the treatment of mature landfill leachate was investigated by testing different system setups. As a first approach, ozonation (O3-only) was ...tested, using a porous ceramic diffuser combined with a bubble column (BC), and the best operational conditions were established for leachate treatment (initial pH = 9.0; inlet ozone dose = 18 mg O3/min). Then, a novel photoreactor (FluHelik) was coupled in series with the bubble column, using a diffuser or a Venturi to inject ozone into the fluid stream. The FluHelik/BC-Venturi setup led to the highest efficiency, treating 50% more leachate than BC-alone using the same ozone dose and reaction time (3 h). Following, the oxidation ability of ozone combined with H2O2 and/or UVC for leachate treatment was assessed. The highest synergistic effect was obtained for the O3/UVC process, with pseudo-first-order rate constant for DOC and COD removal, 2.0 and 1.4 times higher than for the O3-only, respectively. Ozone-driven processes considerably enhanced the leachate biodegradability from 17% to 79% (O3/H2O2), 81% (O3-only), 85% (O3/H2O2/UVC) and 91% (O3/UVC), after a 3 h reaction period. With FluHelik/BC-Venturi system, the O3/UVC process stands out as the most efficient and cost-effective (6.0 €/m3), ensuring an effluent that meets discharge legal limit for COD (150 mg/L) after further biological oxidation.
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•Enhancement of ozone-driven processes in a disruptive and compact photoreactor;•The helical motion of fluid allows for higher ozone utilization rates;•Ozone-driven processes enhanced significantly the leachate biodegradability;•The highest synergistic effect was obtained for the O3/UVC process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Due to the growth in the number of patients and the complexity involved in anticancer therapies, new therapeutic approaches are urgent and necessary. In this context, compounds containing the ...selenium atom can be employed in developing new medicines due to their potential therapeutic efficacy and unique modes of action. Furthermore, tellurium, a previously unknown element, has emerged as a promising possibility in chalcogen-containing compounds. In this study, 13 target compounds (9a–i, 10a–c, and 11) were effectively synthesized as potential anticancer agents, employing a CuI-catalyzed Csp-chalcogen bond formation procedure. The developed methodology yielded excellent results, ranging from 30 to 85%, and the compounds were carefully characterized. Eight of these compounds showed promise as potential therapeutic drugs due to their high yields and remarkable selectivity against SCC-9 cells (squamous cell carcinoma). Compound 10a, in particular, demonstrated exceptional selectivity, making it an excellent choice for cancer cell targeting while sparing healthy cells. Furthermore, complementing in silico and molecular docking studies shed light on their physical features and putative modes of action. This research highlights the potential of these compounds in anticancer treatments and lays the way for future drug development efforts.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
Diabetic nephropathy (DN) is one of the most important causes of chronic renal disease, and the incidence of DN is increasing worldwide. Considering our previous report (Gomes et al., 2014) ...indicating that chronic treatment with oral low-dose quercetin (10 mg/Kg) demonstrated anti-oxidative, anti-apoptotic and renoprotective effects in the C57BL/6J model of DN, we investigated whether this flavonoid could also have beneficial effects in concurrent DN and spontaneous atherosclerosis using the apolipoprotein E-deficient mouse (apoE(-/-)).
Streptozotocin was used to induce diabetes (100 mg/kg/day, 3 days) in male apoE(-/-) mice (8 week-old). After 6 weeks, the mice were randomly separated into DQ: diabetic apoE(-/-) mice treated with quercetin (10 mg/kg/day, 4 weeks, n = 8), DV: diabetic ApoE(-/-) mice treated with vehicle (n = 8) and ND: non-treated non-diabetic mice (n = 8).
Quercetin treatment diminished polyuria (~30%; p < 0.05), glycemia (~25%, p < 0.05), normalized the hypertriglyceridemia. Moreover, this bioflavonoid diminished creatininemia (~30%, p < 0.01) and reduced proteinuria but not to normal levels. We also observed protective effects on the renal structural changes, including normalization of the index of glomerulosclerosis and kidney weight/body weight.
Our data revealed that quercetin treatment significantly reduced DN in hypercholesterolemic mice by inducing biochemical changes (decrease in glucose and triglycerides serum levels) and reduction of glomerulosclerosis. Thus, this study highlights the relevance of quercetin as an alternative therapeutic option for DN, including in diabetes associated with dyslipidemia.
Glycosyl hydrolases are enzymes capable of breaking the glycosidic linkage of polysaccharides and have considerable industrial and biotechnological applications. Driven by the later applications, it ...is frequently desirable that glycosyl hydrolases display stability and activity under extreme environment conditions, such as high temperatures and extreme pHs. Here, we present X-ray structure of the hyperthermophilic laminarinase from Rhodothermus marinus (RmLamR) determined at 1.95 Å resolution and molecular dynamics simulation studies aimed to comprehend the molecular basis for the thermal stability of this class of enzymes. As most thermostable proteins, RmLamR contains a relatively large number of salt bridges, which are not randomly distributed on the structure. On the contrary, they form clusters interconnecting β-sheets of the catalytic domain. Not all salt bridges, however, are beneficial for the protein thermostability: the existence of charge–charge interactions permeating the hydrophobic core of the enzymes actually contributes to destabilize the structure by facilitating water penetration into hydrophobic cavities, as can be seen in the case of mesophilic enzymes. Furthermore, we demonstrate that the mobility of the side-chains is perturbed differently in each class of enzymes. The side-chains of loop residues surrounding the catalytic cleft in the mesophilic laminarinase gain mobility and obstruct the active site at high temperature. By contrast, thermophilic laminarinases preserve their active site flexibility, and the active-site cleft remains accessible for recognition of polysaccharide substrates even at high temperatures. The present results provide structural insights into the role played by salt-bridges and active site flexibility on protein thermal stability and may be relevant for other classes of proteins, particularly glycosyl hydrolases.
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IJS, KILJ, NUK, PNG, UL, UM
9.
Isolation of NDM-producing Providencia rettgeri in Brazil Carvalho-Assef, Ana Paula D'Alincourt; Pereira, Polyana Silva; Albano, Rodolpho Mattos ...
Journal of antimicrobial chemotherapy,
12/2013, Volume:
68, Issue:
12
Journal Article
The use of non-edible oils, waste oils, and animal fats have been investigated as a low-cost feedstock for biodiesel (fatty acid alkyl esters) synthesis. However, these alternative raw materials have ...some drawbacks due to the high content of free fatty acid (FFA). This work aimed to study the continuous enzymatic ethyl esters synthesis, in a solvent-free system, from the reaction of acid soybean oil (acid value, AV, of 0.5, 8.5, 50, and 90) and ethanol using a dual commercial immobilized lipase system (Novozym 435®, Lipozyme TL IM®, Lipozyme RM IM®). Initially, a dual lipase system was used in a single packed-bed reactor (PBR). The blend of Lipozyme TL IM and Novozym 435 had a positive synergistic effect on biodiesel synthesis: an increase of 76% in ethyl ester content was observed after 2 h using refined soybean oil. However, a reduction in the yield was observed in longer reaction times (25 h). Therefore, a continuous reaction system, operated with two different catalytic beds, was investigated. The use of two series reactors allowed high ethyl ester yield (>90%) and high acid conversion (>90%). The reaction using acid soybean oil (50 AV), and Lipozyme RM IM and Novozym 435 reached an ethyl ester content of 95% and 70% after 2 and 25 h, respectively. The results showed that using two different commercial immobilized lipases in intercalated packed-bed reactors enhanced biodiesel synthesis from acid soybean oil. The enzymatic system allows a high fatty acid conversion present in the acidic oil into ethyl ester.
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•The use of two packed-bed reactors in series ensured high levels of ethyl esters.•A synergistic effect was obtained by mixing two different immobilized lipases.•The remaining activity of Novozym 435 was raised with the increasing acidity of the oil.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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