In plant grana thylakoid membranes Photosystem II (PSII) associates with a variable number of antenna proteins (LHCII) to form different types of supercomplexes (PSII-LHCII), whose organization is dynamically adjusted in response to light cues, with the C2S2 more abundant in high-light and the C2S2M2 in low-light. Paired PSII-LHCII supercomplexes interacting at their stromal surface from adjacent thylakoid membranes were previously suggested to mediate grana stacking. Here, we present the cryo-electron microscopy maps of paired C2S2 and C2S2M2 supercomplexes isolated from pea plants grown in high-light and low-light, respectively. These maps show a different rotational offset between the two supercomplexes in the pair, responsible for modifying their reciprocal interaction and energetic connectivity. This evidence reveals a different way by which paired PSII-LHCII supercomplexes can mediate grana stacking at diverse irradiances. Electrostatic stromal interactions between LHCII trimers almost completely overlapping in the paired C2S2 can be the main determinant by which PSII-LHCII supercomplexes mediate grana stacking in plants grown in high-light, whereas the mutual interaction of stromal N-terminal loops of two facing Lhcb4 subunits in the paired C2S2M2 can fulfil this task in plants grown in low-light. The high-light induced accumulation of the Lhcb4.3 protein in PSII-LHCII supercomplexes has been previously reported. Our cryo-electron microscopy map at 3.8 Å resolution of the C2S2 supercomplex isolated from plants grown in high-light suggests the presence of the Lhcb4.3 protein revealing peculiar structural features of this high-light-specific antenna important for photoprotection. 相似文献
The healthy consumers make a strong pressure to natural products that can prevent the chronic diseases and improve the general health status, and therefore an important aspect that have to be considered is the safe level of the nutraceuticals. This study reports the occurrence of Ochratoxin A (OTA) and associated fungal contamination in 35 samples of dried vine fruits imported in the European community potentially used for the development of new nutraceutical supplements. High pressure liquid chromatography analysis identified 18 samples as contaminated by OTA with an average level of 2.6 μg/kg. OTA was measured in 4 samples of currants (mean value of 6.6 μg/kg) and 13 samples of raisins (mean value of 1.4 μg/kg). In one sample of currants and one of raisins from Turkey OTA exceeded the limits set by European Commission of 10 μg/kg, being contaminated with 12.61 and 15.99 μg/kg, respectively. All the positive samples were confirmed by Orbitrap Q Exactive through their molecular weight and the corresponding fragmentation. The worldwide consumption of dried vine fruits contributed to OTA exposure in several group of consumers. In particular, considering the potential nutraceutical approach, this consumption may be represent a severe risk for healthy consumers that consider these products like healthy and salutistic for their contents in antioxidants, flavonoids, and polyphenols. Data reported in this study confirmed the need to regularly monitor mycotoxin levels in these food products and optimize the process of fruits drying in order to reduce the development of toxigenic molds. 相似文献
Epidemiological studies suggested an association between obesity and sleep disturbances. Obstructive sleep apnea is the most prevalent type of obesity-related sleep disorder that lead to an increased risk for numerous chronic health conditions. In addition the increased visceral adipose tissue might be responsible for the secretion of inflammatory cytokines that could contribute to alter the sleep-wake rhythm. Unhealthy food characterized by high consumption of fat and carbohydrate seems to negatively influence the quality of sleep while diet rich of fiber is associated to more restorative and deeper sleep. Although obesity could cause through several pathogenetic mechanisms an alteration of sleep, it has been reported that subjects suffering from sleep disorders are more prone to develop obesity. Experimental laboratory studies have demonstrated that decreasing either the amount or quality of sleep increase the risk of developing obesity. Experimental sleep restriction also causes physiological, hormonal and food behavioral changes that promote a positive energy balance and a compensatory disproportionate increase in food intake, decrease in physical activity, and weight gain. Thus, the aim of this review is to provide observational evidence on the association of obesity with sleep disturbances and viceversa with emphasis on possible pathophysiological mechanisms (hormonal and metabolic) that link these two pathological conditions. 相似文献
Selective MMP inhibitors : Eleven α‐sulfonylphosphonates were synthesized and tested as MMP inhibitors. The IC50 values for most of them are in the nanomolar range against MMP‐2, ‐8, ‐13, and ‐14, with an interesting selectivity profile versus MMP‐9.
Delayed failure and creep behavior of high-purity Si3N4 sintered without additives with a mean grain size of 1 μm has been measured at 1400°C. Lifetime under 300 MPa was >240 h, which showed good agreement with the value predicted in our previous report. Creep strain rate ranged from 1 × 10−5 to 3 × 10−5 h−1 between 200 and 360 MPa. These values demonstrate the excellent potential of high-purity Si3N4 materials for structural application up to 1400°C. 相似文献
A method based on reversed-phase high-performance liquid chromatography with fluorescence detector has been developed for the determination of tocopherols in vegetable oils. Oils were diluted in acetonitrile/tetrahydrofuran (THF) and injected directly onto HyPurity C18 column. Methanol and THF (90:10) mixture was used as a mobile phase. Tocopherols were detected by fluorescence detector. The method had good limit of detection (LOD) (7 ng/g for α-tocopherol and 6 ng/g for β-, γ- and δ-tocopherols) and reproducibility (CV% < 2.8%). 相似文献
The distribution of aflatoxin M1 (AFM1) has been investigated in samples of whey, curd and a typical hard and long maturing cheese like Grana Padano (ripened for twelve months), produced with naturally contaminated milk in a range of 30–98 ng AFM1/kg. AFM1 determinations were carried out on 25 samples of each product by reverse-phase HPLC and fluorescence detection with post-column derivatisation, after a preliminary C18-SPE clean-up. Experimental results show that, in comparison to milk, AFM1 concentration levels increased both in curd (3-fold) and in long maturing cheese (4.5-fold), while AFM1 occurrence in whey decreased by 40%. 相似文献
The present study focused on the application of pulsed electric fields (PEF) as an innovative pre-treatment technique to improve the recovery of polyphenols from two food by-products, cocoa bean shell (CBS) and coffee silver skin (CS). The effect of the different operating parameters on the extraction of polyphenols was optimised using the response surface methodology statistical approach. The optimised methodology was compared with conventional extraction and applied to several CBS and CS samples to classify the samples according to origin, variety and industrial treatment. PEF-assisted extraction had higher (approximately 20%) recovery yields of polyphenols and methylxanthines than conventional extraction. Finally, the results highlighted that the composition of bioactive compounds from different extracts of CBS and CS and their antioxidant properties depended on the origin, variety and industrial processing of the raw material. These by-products may be a promising source of natural compounds, with potential applications on food and health sectors. 相似文献
Microwave-assisted sample digestion and inductively coupled plasma-mass spectrometry (ICP-MS) were considered for exploring major and trace elements in the Mediterranean Sepia ink. The present work aims to (a) fully validate the employed ICP-MS method and compare the Hg determinations by ICP-MS with those obtained by a direct mercury analyzer (DMA) and (b) interpret quantitative data by chemometrics and perform a risk/benefit analysis for assessing the quality/safety of Sepia ink. DMA gave Hg determinations similar to the ICP-MS counterpart (p > 0.05), confirming its reliability for food analysis. Sepia ink demonstrated to be both a reservoir of “healthy” elements and a sink of potential toxic metals. In fact, a good contribution of major and essential trace metals to the established RDAs was revealed, and, at the same time, potentially toxic elements showed to accumulate depending upon the environmental conditions, although not representing a risk for human consumers. 相似文献