341 research outputs found

    Epigenetics as an Evolutionary Tool for Centromere Flexibility

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    Centromeres are the complex structures responsible for the proper segregation of chromosomes during cell division. Structural or functional alterations of the centromere cause aneuploidies and other chromosomal aberrations that can induce cell death with consequences on health and survival of the organism as a whole. Because of their essential function in the cell, centromeres have evolved high flexibility and mechanisms of tolerance to preserve their function following stress, whether it is originating from within or outside the cell. Here, we review the main epigenetic mechanisms of centromeres’ adaptability to preserve their functional stability, with particular reference to neocentromeres and holocentromeres. The centromere position can shift in response to altered chromosome structures, but how and why neocentromeres appear in a given chromosome region are still open questions. Models of neocentromere formation developed during the last few years will be hereby discussed. Moreover, we will discuss the evolutionary significance of diffuse centromeres (holocentromeres) in organisms such as nematodes. Despite the differences in DNA sequences, protein composition and centromere size, all of these diverse centromere structures promote efficient chromosome segregation, balancing genome stability and adaptability, and ensuring faithful genome inheritance at each cellular generation

    Influence of Chemical and Physical Variables on 87Sr/86Sr Isotope Ratios Determination for Geographical Traceability Studies in the Oenological Food Chain

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    This study summarizes the results obtained from a systematic and long-term project aimed at the development of tools to assess the provenance of food in the oenological sector. 87Sr/86Sr isotope ratios were measured on a representative set of soils, branches, and wines sampled from the Chianti Classico wine production area. In particular, owing to the high spatial resolution of the 87Sr/86Sr ratio in the topsoil, the effect of two mill techniques for soil pretreatment was investigated to verify the influence of the particle dimension on the measured isotopic ratios. Samples with particle sizes ranging from 250 to less than 50 m were investigated, and the extraction was performed by means of the DIN 19730 procedure. For each sample, the Sr isotope ratio was determined as well. The obtained results showed that the 87Sr/86Sr ratio is not influenced by soil particle size and may represent an effective tool as a geographic provenance indicator for the investigated product

    Reactivity of platinum(II) triphenylphosphino complexes with nitrogen donor divergent ligands

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    Dinuclear platinum(II) complexes [{PtCl2(PPh3)}2(μ-N–N)], where N–N is a divergent bidentate nitrogen ligand, were prepared by reacting cis-[PtCl2(PPh3)(NCMe)] with N–N in a Pt/N–N molar ratio 2. The (trans,trans)-isomers were obtained as kinetic products and recovered in good yields and high purity {1, N–N = pyrazine (pyrz); 2, N–N = 4,4′-bipyridyl (bipy); 3, N–N = piperazine (pipz); 4, N–N = p-xylylendiamine (xylN2)}. Cis-[PtCl2(PPh3)(NCMe)] was also reacted with the tridentate divergent ligand 2,4,6-tris-(pyrid-4′-yl)1,3,5-triazine (py3TRIA) in molar ratio 3 with formation of the trinuclear (trans,trans,trans)-[{PtCl2(PPh3)}3(μ-py3TRIA)], 5. On the other hand, the treatment of cis-[PtCl2(PPh3)(NCMe)] with the monodentate pyridine (py) produced a mixture of both trans-[PtCl2(PPh3)(py)] (6a) and cis-[PtCl2(PPh3)(py)] (6b). The reactions of cis-[PtCl2(PPh3)(NCMe)] with N–N = pyrz, bipy, pipz, carried out with a Pt/N–N molar ratio 1, were monitored by 31P NMR spectroscopy. Equilibria were observed in solution, involving dinuclear (trans–trans)-[{PtCl2(PPh3)}2(μ-N–N)], mononuclear [PtCl2(PPh3)(N–N)] and free N–N. The addition of an excess of the divergent ligand allowed the complete conversion to the corresponding mononuclear complexes. With the heteroaromatic ligands both geometric isomers were observed (7a, 7b and 8a, 8b, for pyrz and bipy derivatives, respectively) while with pipz the trans-isomer only was detected, 9. In the system involving bipy, the scarcely soluble dinuclear (cis,cis)-[{PtCl2(PPh3)}2(μ-bipy)], 2b, was also obtained. Products 2, 2b, 3·2(CHCl3) and 6a·0.5(C2H4 Cl2) were structurally characterized by single crystal X-ray diffraction methods

    The way to ultrafast, high-throughput enantioseparations of bioactive compounds in liquid and supercritical fluid chromatography

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    Until less than 10 years ago, chiral separations were carried out with columns packed with 5 or 3 μm fully porous particles (FPPs). Times to resolve enantiomeric mixtures were easily larger than 30 min, or so. Pushed especially by stringent requirements from medicinal and pharmaceutical industries, during the last years the field of chiral separations by liquid chromatography has undergone what can be defined a “true revolution”. With the purpose of developing ever faster and efficient method of separations, indeed, very efficient particle formats, such as superficially porous particles (SPPs) or sub-2 μm FPPs, have been functionalized with chiral selectors and employed in ultrafast applications. Thanks to the use of short column (1–2 cm long), packed with these extremely efficient chiral stationary phases (CSPs), operated at very high flow rates (5–8 mL/min), resolution of racemates could be accomplished in very short time, in many cases less than 1 s in normal-, reversed-phase and HILIC conditions. These CSPs have been found to be particularly promising also to carry out high-throughput separations under supercritical fluid chromatography (SFC) conditions. The most important results that have been recently achieved in terms of ultrafast, high-throughput enantioseparations both in liquid and supercritical fluid chromatography with particular attention to the very important field of bioactive chiral compounds will be reviewed in this manuscript. Attention will be focused not only on the latest introduced CSPs and their applications, but also on instrumental modifications which are required in some cases in order to fully exploit the intrinsic potential of new generation chiral columns

    Synthesis and reactivity of platinum(II) triphenylphosphino complexes with aromatic aldoximes

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    trans-[Pt(ÎĽ-Cl)Cl(PPh3)]2 reacted with arylaldoximes in 1,2-dichloroethane to afford [PtCl2(PPh3){N(OH)=CHAr}] (Ar = 3,4-dimethoxyphenyl, 1-naphthyl, 9-anthryl) where aldoxime ligands are N-coordinated to platinum. The obtained complexes are soluble in chlorinated solvents, where they afford equilibrium mixtures of cis,trans and/or (E),(Z) isomers. Equilibria in solution were studied by 31P-NMR spectroscopy and solid state structural data were obtained by single crystal X ray diffraction studies. The reactivity of [PtCl2(PPh3){N(OH)=CHAr}] complexes with basic aqueous solutions was studied, under liquid-liquid phase transfer catalysis conditions. The outcome of the reaction depends on the stereochemistry of the precursors: cis,(Z)-isomers promptly undergo cyclization to the corresponding dinuclear derivatives [Pt{ÎĽ-(2-N,O)}- {N(O)=CHAr}Cl(PPh3)]2, where two aldoximate ligands symmetrically bridge two metal centers

    Sedimentology and composition of sands injected during the seismic crisis of May 2012 (Emilia, Italy): clues for source layer identification and liquefaction regime

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    InMay 2012widespread sand blows formed along buried channels in the eastern sector of the Po Plain (Northern Italy) as a consequence of a series of seismic eventswith main shocks ofMw6.1 and 5.9. At San Carlo (Ferrara) a trench dug a few week after the earthquakes exposed sand dikes cutting through an old Reno River channel– levee system that was diverted in the 18th century and was deposited starting from the 14th century (unit A). This sequence overlies a Holocene muddy floodplain deposits and contains scattered sandy channel deposits (unit B) and a Pleistocene channel sand unit (unit C). Sands with inverse and normal grading, concave layering and vertical lamination coexisting along the dikes suggest multiple rhythmic opening and closing of the fractures that were injected and filled by a slurry of sand during the compression pulses, and emptied during the extension phase. The pulse mechanism may have lasted for several minutes and formed well stratified sand volcanoes structures that formed at the top of the fractures. Sands fromdikes and fromthe various units showwell defined compositional fields from lithoarenitic to quartz-feldspar-rich compositions. Sands from the old Reno levee and channel fill (unit A) have abundant lithic fragments derived fromthe erosion of Apennine sedimentary carbonate and terrigenous successions. Composition of the sand filling the dikes showclear affinities with sand layers of the old Reno River channel (Unit A) and clearly differ from any sand from deeper Holocene and Pleistocene layers (Unit B and C),which are richer in quartz and feldspar and poorer in sedimentary lithic fragments. Sorting related to sediment flux variations did not apparently affect the sand composition across the sedimentary structures. Textural and compositional data indicate that the liquefaction processes originated from a relatively shallow source consisting of channel sands located within Unit A at 6.8.to 7.5 m depth

    Status of correlation between BMI and response to immunocheck-point inhibitor in advanced non-small-cell lung cancer

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    Recently, clinical evidence has raised BMI as an emerging prognostic factor for immunotherapy, regardless of cancer types. In this article we rewirw current data about correlation between BMI and response to immunocheck-point inhibitor in advanced non-small-cell lung cance

    DISTRIBUTION OF HEAT STABILIZERS IN PLASTICIZED PVC-BASED BIOMEDICAL DEVICES: TEMPERATURE AND TIME EFFECTS

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    Thermoplastic polymers can be viewed as a dynamic framework in which additives allocation is strongly dependent on the system' chemistry. Considering the complexity of the distribution phenomena that may occur in plastics obtained by blending polymeric resins with different additives, this work constitutes an attempt to the description of the behavior of PVC heat stabilizers (calcium and zinc carboxylates), as regard temperature and time. Thanks to the Fourier Transform Infrared Spectroscopy, it is possible to observe a first decreasing trend of the additives related IR-bands as a function of the increasing temperature and the higher the temperature the faster the decrease of the heat stabilizers intensities bands is, with respect to time. Additives distribution in not sterilized, sterilized, aged not sterilized and aged sterilized materials have been investigated to determine their behavior with respect to temperature, from 30 to 120°C, and time. A simulated supplementary aging process equivalent to 9 months aging was carried out on aged not sterilized and aged sterilized materials to gain more data on the transport/reaction phenomena these additives in the plastic material. Experimental evidences allow hypothesizing that reaction and redistribution phenomena probably concur to determine the additives allocation in PVC as a function of temperature and time

    A convenient synthesis of highly luminescent lanthanide 1D-zigzag coordination chains based only on 4,4′-bipyridine as connector

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    The coordination polymers View the MathML source·C7H8 (Ln = Eu, β-dik = dbm, tta, hfac; Ln = Tb; β-dik = dbm; Hdbm = dibenzoylmethane, Htta = thenoyltrifluoroacetone, Hhfac: hexafluoroacetylacetone) were easily assembled in mild conditions and high yields starting from the anhydrous lanthanide β-diketonates as nodes and 4,4′-bipyridine (bpy) as connector. X-ray single crystal studies have shown zigzag extended chains where lanthanide centres are 8-coordinated in a distorted square-antiprismatic geometry. Photoluminescence studies show bright red europium emission and spectral features dependent on the topology of the polymeric chains
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