Crystal Structure of a 9-Subunit Archaeal Exosome in Pre-Catalytic States of the Phosphorolytic Reaction

The RNA exosome is an important protein complex that functions in the 3′ processing and degradation of RNA in archaeal and eukaryotic organisms. The archaeal exosome is functionally similar to bacterial polynucleotide phosphorylase (PNPase) and RNase PH enzymes as it uses inorganic phosphate (Pi) to processively cleave RNA substrates releasing nucleoside diphosphates. To shed light on the mechanism of catalysis, we have determined the crystal structures of mutant archaeal exosome in complex with either Pi or with both RNA and Pi at resolutions of 1.8 Å and 2.5 Å, respectively. These structures represent views of precatalytic states of the enzyme and allow the accurate determination of the substrate binding geometries. In the structure with both Pi and RNA bound, the Pi closely approaches the phosphate of the 3′-end nucleotide of the RNA and is in a perfect position to perform a nucleophilic attack. The presence of negative charge resulting from the close contacts between the phosphates appears to be neutralized by conserved positively charged residues in the active site of the archaeal exosome. The high degree of structural conservation between the archaeal exosome and the PNPase including the requirement for divalent metal ions for catalysis is discussed

Neural stem cell systems: physiological players or in vitro entities?

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Selecting the Optimal Use of the Geothermal Energy Produced with a Deep Borehole Heat Exchanger: Exergy Performance

The geothermal sector has a strength point with respect to other renewable energy sources: the availability of a wide range of both thermal and power applications depending on the source temperature. Several researches have been focused on the possibility to produce geothermal energy without brine extraction, by means of a deep borehole heat exchanger. This solution may be the key to increase the social acceptance, to reduce the environmental impact of geothermal projects, and to exploit unconventional geothermal systems, where the extraction of brine is technically complex. In this work, exergy efficiency has been used to investigate the best utilization strategy downstream of the deep borehole heat exchanger. Five configurations have been analyzed: a district heating plant, an absorption cooling plant, an organic Rankine cycle, a cascade system composed of district heat and absorption chiller, and a cascade system composed of the organic Rankine plant. District heating results in a promising and robust solution: it ensures high energy capacities per well depth and high exergy efficiency. Power production shows performances in line with typical geothermal binary plants, but the system capacity per well depth is low and the complexity increases both irreversibilities and sensibility to operative and source conditions

A comprehensive exergy evaluation of a deep borehole heat exchanger coupled with a ORC plant: the case study of Campi Flegrei

The paper presents a comprehensive energy and exergy analysis of a possible geothermal power plant located in the geothermal district of Campi Flegrei (Italy), made of a coaxial WellBore Heat eXchanger coupled to an Organic Rankine Cycle. We have accounted for all system components: the ground source, the WellBore Heat eXchanger, the Organic Rankine Cycle cycle, and cooling system. The energy and exergy performance indexes of each subsystems and overall system have been evaluated, thus calculating the net power, the First-Law efficiency, the Second-Law efficiency, the irreversibilities. The results indicate a good potential of the WellBore Heat eXchanger – Organic Rankine Cycle technology in the area, as the estimated performances have similar values to those of classical binary geothermal power plants: a First-Law efficiency of 11.67% and a Second-Law efficiency of about 43.80%. The overall system performances decrease respectively to 10.62% due to the fans energy requirements in the cooling tower and to 23.15% due to the large exergy destruction occurring in the WellBore Heat eXchanger. A deep exergy analysis of the WellBore Heat eXchanger has highlighted that the overall irreversibility is strongly affected by the insulation performance between the two coaxial pipes and by the temperature deviation between the ground and the fluid. The latter one is mainly due to the continuous heat extraction from the geothermal source, therefore proposed improvement strategies consist of both the increasing of thermal resistance of the material insulating the upward pipe and the reduction of the equivalent thermal radius of the well optimizing the heat extraction profiles over the plant lifetime

Selecting the optimal use of the geothermal energy produced with a deep borehole heat exchanger. Exergy performance

The geothermal sector has a strength point with respect to other renewable energy sources: the availability of a wide range of both thermal and power applications depending on the source temperature. Several researches have been focused on the possibility to produce geothermal energy without brine extraction, by means of a deep borehole heat exchanger. This solution may be the key to increase the social acceptance, to reduce the environmental impact of geothermal projects, and to exploit unconventional geothermal systems, where the extraction of brine is technically complex. In this work, exergy efficiency has been used to investigate the best utilization strategy downstream of the deep borehole heat exchanger. Five configurations have been analyzed: a district heating plant, an absorption cooling plant, an organic Rankine cycle, a cascade system composed of district heat and absorption chiller, and a cascade system composed of the organic Rankine plant. District heating results in a promising and robust solution: it ensures high energy capacities per well depth and high exergy efficiency. Power production shows performances in line with typical geothermal binary plants, but the system capacity per well depth is low and the complexity increases both irreversibilities and sensibility to operative and source conditions

Decrease of sexual organ reciprocity between heterostylous primrose species, with possible functional and evolutionary implications

Background and Aims Heterostyly is a floral polymorphism that has fascinated evolutionary biologists since Darwin's seminal studies on primroses. The main morphological characteristic of heterostyly is the reciprocal placement of anthers and stigmas in two distinct (distyly) floral morphs. Variation in the degree of intermorph sexual reciprocity is relatively common and known to affect patterns of pollen transfer within species. However, the partitioning of sexual organ reciprocity within and between closely related species remains unknown. This study aimed at testing whether intermorph sexual reciprocity differs within vs. between primrose species that hybridize in nature and whether the positions of sexual organs are correlated with other floral traits. Methods Six floral traits were measured in both floral morphs of 15 allopatric populations of Primula elatior, P. veris and P. vulgaris, and anther-stigma reciprocity was estimated within and between species. A combination of univariate and multivariate approaches was used to test whether positions of reproductive organs were less reciprocal between than within species, to assess correlations between sexual organ positions and other corolla traits, and to quantify differences between morphs and species. Key Results The three species were morphologically well differentiated in most floral traits, except that P. veris and P. vulgaris did not differ significantly in sexual organ positions. Overall, lower interspecific than intraspecific sexual organ reciprocity was detected. This decrease was marked between P. elatior and P. vulgaris, intermediate and variable between P. elatior and P. veris, but negligible between P. veris and P. vulgaris. Conclusions Differences in anther and stigma heights between the analysed primrose species were of the same magnitude or larger than intraspecific differences that altered pollen flow within other heterostylous systems. Therefore, it is possible to suggest that considerable reductions of sexual organ reciprocity between species may lower interspecific pollen flow, with potential effects on reproductive isolatio

Oral mucosal lesions in electronic cigarettes consumers versus former smokers

Electronic cigarettes (ECs) have become very popular in recent years. However, many uncertainties remain about their side effects. This study aims to evaluate the prevalence and characteristics of oral mucosal lesions (OMLs) in former smokers compared to ECs consumers

Oral mucosal lesions in teenagers: a cross-sectional study

Aim The aim of this study was to evaluate the distribution of oral mucosal lesions (OMLs) in a wide sample of adolescents. Methods A retrospective cross-sectional study was carried out examining all medical records of adolescents (aged 13-18 years) treated at the Dental Clinic of the University of Brescia (Italy) in the period from 2008 to 2014. Cases with OMLs were selected. Data regarding age, gender, type of OML, bad habits, systemic chronic diseases were collected. Results A total of 6.374 medical records (mean age 15.2+-1.7 years) were examined. We found 1544 cases (31.7%) of oral mucosal lesions; 36 different types of mucosal alterations were detected and the most frequent were: aphthous ulcers (18%), traumatic ulcerations (14.3%), herpes simplex virus (11%), geographic tongue (9.6%), candidiasis (5.5%), and morsicatio buccarum (4.7%). Papilloma virus lesions (1.7%), piercing-related lesions (4%), multiform erythema (0.13%), oral lichen planus (0.13%) and granular cell tumour (0.06%) were also diagnosed. Conclusions The prevalence of OMLs in adolescents are different from those in children and, in some conditions, it could increase with age