The ubiquitin-proteasome system plays a pivotal role in the sequence of events leading to cell division known as the cell cycle. Not only does ubiquitin-mediated proteolysis constitute a critical ...component of the core oscillator that drives the cell cycle in all eukaryotes, it is also central to the mechanisms that ensure that the integrity of the genome is maintained. These functions are primarily carried out by two families of E3 ubiquitin ligases, the Skp/cullin/F-box-containing and anaphase-promoting complex/cyclosome complexes. However, beyond those functions associated with regulation of central cell cycle events, many peripheral cell cycle-related processes rely on ubiquitylation for signaling, homeostasis, and dynamicity, involving additional types of ubiquitin ligases and regulators. We are only beginning to understand the diversity and complexity of this regulation.
Urban grasslands are crucial for biodiversity and ecosystem services in cities, while little is known about their multifunctionality under climate change. Thus, we investigated the effects of ...simulated climate change, i.e., increased CO2 and temperature, and reduced precipitation, on individual functions and overall multifunctionality in mesocosm grasslands sown with forbs and grasses in four different proportions aiming at mimicking road verge grassland patches. Climate change scenarios RCP2.6 (control) and RCP8.5 (worst-case) were simulated in walk-in climate chambers of an ecotron facility, and watering was manipulated for normal vs. reduced precipitation. We measured eight indicator variables of ecosystem functions based on below- and aboveground characteristics. The young grassland communities responded to higher CO2 and warmer conditions with increased vegetation cover, height, flower production, and soil respiration. Lower precipitation affected carbon cycling in the ecosystem by reducing biomass production and soil respiration. In turn, the water regulation capacity of the grasslands depended on precipitation interacting with climate change scenario, given the enhanced water efficiency resulting from increased CO2 under RCP8.5. Multifunctionality was negatively affected by reduced precipitation, especially under RCP2.6. Trade-offs arose among single functions that performed best in either grass- or forb-dominated grasslands. Grasslands with an even ratio of plant functional types coped better with climate change and thus are good options for increasing the benefits of urban green infrastructure. Overall, the study provides experimental evidence of the effects of climate change on the functionality of urban ecosystems. Designing the composition of urban grasslands based on ecological theory may increase their resilience to global change.
DNA replication must be precisely controlled in order to maintain genome stability. Transition through cell cycle phases is regulated by a family of Cyclin-Dependent Kinases (CDKs) in association ...with respective cyclin regulatory subunits. In normal cell cycles, E-type cyclins (Cyclin E1 and Cyclin E2,
and
genes) associate with CDK2 to promote G1/S transition. Cyclin E/CDK2 complex mostly controls cell cycle progression and DNA replication through phosphorylation of specific substrates. Oncogenic activation of Cyclin E/CDK2 complex impairs normal DNA replication, causing replication stress and DNA damage. As a consequence, Cyclin E/CDK2-induced replication stress leads to genomic instability and contributes to human carcinogenesis. In this review, we focus on the main functions of Cyclin E/CDK2 complex in normal DNA replication and the molecular mechanisms by which oncogenic activation of Cyclin E/CDK2 causes replication stress and genomic instability in human cancer.
A method for determining thallium in water samples via solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (SS HR-CS GF AAS) after preconcentration using ...chromatographic filter paper as a solid support was proposed. The effects of pH, stirring time, and sample volume in the analyte preconcentration step were studied. The presence of potential interferences in the sample and the type of masking agent were also examined. In the proposed procedure, the sample was placed in contact with the solid phase in a polypropylene tube, and after stirring for 3 min, thallium determination was performed via HR-CS GF AAS directly on chromatographic filter paper. A preconcentration factor of 55, a precision of 9.4% (n = 10; 10 μg L−1), a limit of detection of 0.018 μg L−1, and a limit of quantification of 0.059 μg L−1 were achieved. Analyte addition and recovery tests were performed, and the results ranged from 91% to 110%. The accuracy of the method was evaluated by analyzing a water reference material. The procedure was used to determine thallium in water samples collected in Barreiras, Bahia, Brazil. The results were compared with those obtained using inductively coupled plasma‒mass spectrometry (ICP‒MS). Thallium concentrations in the analyzed samples ranged from <0.059 to 0.80 μg L−1.
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•A method for Tl determination in water samples using SS HR-CS GF AAS is presented.•Thallium preconcentration using chromatographic filter paper as a solid phase was performed.•Thallium determination was carried out via HR-CS GF AAS directly on chromatographic paper.•This method was used to analyze river water samples.
This review focuses on the determination of uranium using spectroanalytical techniques that are aimed at total determination such as flame atomic absorption spectrometry (FAAS), electrothermal atomic ...absorption spectrometry (ETAAS), inductively coupled plasma optical emission spectrometry (ICP-OES); and inductively coupled plasma mass spectrometry (ICP-MS) that also enables the determination of uranium isotopes. The advantages and shortcomings related to interferences, precision, accuracy, sample type and equipment employed in the analysis are taken into account, as well as the complexity and costs (i.e., acquisition, operation and maintenance) associated with each of the techniques. Strategies to improve their performance that employ separation and/or preconcentration steps are considered, with an emphasis given to solid-phase extraction because of its advantages compared to other preconcentration procedures.
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•Synthesis of mercaptopropionic acid (MPA)-capped CdTe QDs in aqueous medium.•Quenching effect of iron on MPA-capped CdTe QDs fluorescence signal.•Selective determination of iron in ...biodiesel of vegetable or animal origin.•Use of inorganic aqueous standards in the calibration method.•High analytical sensitivity, wide dynamic working range and fairly low cost.
The determination of trace elements in biodiesel is essential to assess oil qualities, identify adulterations and prevent undesirable effects in environment and in humans. However, due to the low sample concentration, sensitive instrumental techniques are required.
In this work an effective and simple quantification method using water-soluble mercaptopropionic acid (MPA)-capped CdTe quantum dots (QDs) was for the first time implemented for the fluorescence quantification of iron in biodiesel obtained from different vegetable oils and fat. The developed methodology was based on the iron capacity to establish surface interactions with the nanocrystals that result in a quenching of the fluorescence intensity (F0−F), proportional to the iron concentration. Size and concentration of QDs, concentration and pH of the buffer solution showed a strong effect on the quenching efficiency influencing linear working range and sensitivity of the methodology.
An ultrasonic bath was used for the extraction of iron from oil samples with a mixture of 1:1 (v/v) concentrated HCl and H2O2. The extraction efficiency was approximately 100% after 50min of ultrasound.
Under the optimized experimental conditions, a linear working range was obtained for iron concentrations from 4.16 to 100.0μgL−1 (R=0.9996, n=6). The determined detection limit (LOD) was about 1.25μgL−1. Six biodiesel samples were analyzed by the proposed methodology, and the results revealed good agreement with those obtained through a high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) comparison procedure. Relative deviations lower than 4.5% were achieved, and the application of a paired Student’s t-test, confirmed the absence of any statistical difference for a confidence level of 95% (n=5). Recoveries varied from 90.2% to 105.2%. The slopes of the analytical curves obtained with different matrices showed that the quantification of the analytes was not influenced by matrix effects. The quenching mechanism of CdTe QDs is discussed. The accuracy, precision and operational simplicity of the method, without additional electronic devices, demonstrated an excellent alternative for determination of iron in biodiesel samples.
Dynamic reversed-phase liquid-liquid microextraction (RP-LLME) is proposed to prepare vegetable oil samples for posterior determination of cadmium, chromium, manganese, and nickel by energy ...dispersive X-ray fluorescence (EDXRF) spectrometry. The microextraction procedure was based on a dynamic system in which the sample flowed through the acceptor phase in an extraction chamber. After extraction, the rich phase was deposited on filter paper and subjected to metal determination by EDXRF. The following parameters were optimized: type and concentration of the acceptor phase, sample flow rate, and extraction time. Nitric acid 0.1 mol L−1, a sample flow rate of 10 mL min−1, and an extraction time of 15 min were employed in the recommended procedure. Under these conditions, limits of quantification of 6, 7, 8, and 11 μg kg−1 were obtained for Cd, Cr, Mn, and Ni, respectively. The preconcentration factors obtained were 100 (Cd), 65 (Cr), 82 (Mn), and 74 (Ni). The developed method was applied to determine Cd, Cr, Mn, and Ni vegetable oil samples.
•A method for multi-element determination in vegetable oils by EDXRF is presented.•Dynamic RP-LLME was employed for analyte separation from the sample.•The microextraction was based on a dynamic system in an extraction chamber.•The method was applied to determine Cd, Cr, Mn, and Ni in vegetable oils.
•HR-CS GF MAS was employed for indirect determination of phospholipids.•Soybean lecithin samples were analyzed.•Phosphorus was determined via molecular absorption of phosphorus monoxide.•Simple ...sample preparation by dilution with MIBK.
This paper presents a method for determining phospholipids in soybean lecithin samples by phosphorus determination using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) via molecular absorption of phosphorus monoxide. Samples were diluted in methyl isobutyl ketone. The best conditions were found to be 213.561nm with a pyrolysis temperature of 1300°C, a volatilization temperature of 2300°C and Mg as a chemical modifier. To increase the analytical sensitivity, measurement of the absorbance signal was obtained by summing molecular transition lines for PO surrounding 213nm: 213.561, 213.526, 213.617 and 213.637nm. The limit of detection was 2.35mgg−1 and the precision, evaluated as relative standard deviation (RSD), was 2.47% (n=10) for a sample containing 2.2% (w/v) phosphorus. The developed method was applied for the analysis of commercial samples of soybean lecithin. The determined concentrations of phospholipids in the samples varied between 38.1 and 45% (w/v).
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•1,3-propanediol as a sustainable product obtained from biodiesel-derived glycerol hydrogenolysis.•Market and industrial routes for the production of 1,3-propanediol.•Analysis of ...metallic and acid sites for the production of 1,3-propanediol.•Influence of Lewis/Brønsted acid ratio in glycerol conversion and 1,3-propanediol selectivity.
1,3-propanediol (1,3-PDO) is obtained from renewable and environmentally friendly glycerol. The current industrial production uses high cost genetically modified microorganisms. Researchers have studied heterogeneous catalysts for more efficient processes leading to higher competitiveness in the 1,3-PDO market. In this context, a review of studies involving chemical routes for its production was performed, evaluating process variables and, in particular, the influence of active acid and metallic phases on the activity and selectivity to the desired product. Platinum, iridium, and copper were verified to be the most promising metals. Brønsted sites are responsible for the higher selectivity to 1,3-PDO, while the reaction rate strongly depends on Lewis sites since glycerol adsorption takes place in these sites. Moreover, in order to decrease operating costs, important parameters such as temperature, glycerol concentration in the feed stream and the reactor type must be optimized.
In this review, general aspects of the combination of the solid phase extraction (SPE) with energy dispersive X-ray fluorescence spectrometry (EDXRF) for multielement determination are presented. ...Derivations of SPE, such as dispersive solid phase extraction (DSPE), dispersive micro-solid phase extraction (DµSPE), and dispersive magnetic micro-solid phase extraction DM-µSPE are also presented, showing the possibility of direct analysis of the solid phase. The sorbents, advantages, disadvantages, and the analytical characteristics of the combination followed by direct determination of analytes retained on the solid phase are discussed. Furthermore, the perspectives of this analytical arrangement are presented.
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