89 research outputs found
1,3,5,7-TetraÂkis(4-iodoÂphenÂyl)adamantane benzene tetraÂsolvate
The title molÂecule, C34H28I4·4C6H6, has crystallographic symmetry and crystallizes with four symmetry-related benzene solvent molÂecules. The phenyl group is eclipsed with one of the adamantane CâC bonds. The tetraÂphenylÂadamantane units and the benzene solvent molÂecules are connected by weak interÂmolecular phenÂylâbenzene CâHâŻÏ and benzeneâbenzene CâHâŻÏ interÂactions. In the crystal, molÂecules are linked along the c-axis direction via the iodoÂphenyl groups by a combination of weak interÂmolecular IâŻI [3.944â
(1)â
Ă
] and IâŻÏ(phenÂyl) [3.608â
(6) and 3.692â
(5)â
Ă
] interÂactions
Glancing through the debris disk: Photometric analysis of DE Boo with CHEOPS
Aims. DE Boo is a unique system, with an edge-on view through the debris disk around the star. The disk, which is analogous to the Kuiper belt in the Solar System, was reported to extend from 74 to 84 AU from the central star. The high photometric precision of the Characterising Exoplanet Satellite (CHEOPS) provided an exceptional opportunity to observe small variations in the light curve due to transiting material in the disk. This is a unique chance to investigate processes in the debris disk.
Methods. Photometric observations of DE Boo of a total of four days were carried out with CHEOPS. Photometric variations due to spots on the stellar surface were subtracted from the light curves by applying a two-spot model and a fourth-order polynomial. The photometric observations were accompanied by spectroscopic measurements with the 1m RCC telescope at Piszkésteto and with the SOPHIE spectrograph in order to refine the astrophysical parameters of DE Boo.
Results. We present a detailed analysis of the photometric observation of DE Boo. We report the presence of nonperiodic transient features in the residual light curves with a transit duration of 0.3â0.8 days. We calculated the maximum distance of the material responsible for these variations to be 2.47 AU from the central star, much closer than most of the mass of the debris disk. Furthermore, we report the first observation of flaring events in this system.
Conclusions. We interpreted the transient features as the result of scattering in an inner debris disk around DE Boo. The processes responsible for these variations were investigated in the context of interactions between planetesimals in the system
Glancing through the debris disk: Photometric analysis of DE Boo with CHEOPS
Aims: DE Boo is a unique system, with an edge-on view through the debris disk around the star. The disk, which is analogous to the Kuiper belt in the Solar System, was reported to extend from 74 to 84 AU from the central star. The high photometric precision of the Characterising Exoplanet Satellite (CHEOPS) provided an exceptional opportunity to observe small variations in the light curve due to transiting material in the disk. This is a unique chance to investigate processes in the debris disk. Methods: Photometric observations of DE Boo of a total of four days were carried out with CHEOPS. Photometric variations due to spots on the stellar surface were subtracted from the light curves by applying a two-spot model and a fourth-order polynomial. The photometric observations were accompanied by spectroscopic measurements with the 1m RCC telescope at Piszkésteto and with the SOPHIE spectrograph in order to refine the astrophysical parameters of DE Boo. Results: We present a detailed analysis of the photometric observation of DE Boo. We report the presence of nonperiodic transient features in the residual light curves with a transit duration of 0.3-0.8 days. We calculated the maximum distance of the material responsible for these variations to be 2.47 AU from the central star, much closer than most of the mass of the debris disk. Furthermore, we report the first observation of flaring events in this system. Conclusions: We interpreted the transient features as the result of scattering in an inner debris disk around DE Boo. The processes responsible for these variations were investigated in the context of interactions between planetesimals in the system. This article uses data from CHEOPS programme CH_PR100010
45S rDNA Regions Are Chromosome Fragile Sites Expressed as Gaps In Vitro on Metaphase Chromosomes of Root-Tip Meristematic Cells in Lolium spp
BACKGROUND: In humans, chromosome fragile sites are regions that are especially prone to forming non-staining gaps, constrictions or breaks in one or both of the chromatids on metaphase chromosomes either spontaneously or following partial inhibition of DNA synthesis and have been well identified. So far, no plant chromosome fragile sites similar to those in human chromosomes have been reported. METHODS AND RESULTS: During the course of cytological mapping of rDNA on ryegrass chromosomes, we found that the number of chromosomes plus chromosome fragments was often more than the expected 14 in most cells for Lolium perenne L. cv. Player by close cytological examination using a routine chromosome preparation procedure. Further fluorescent in situ hybridization (FISH) using 45S rDNA as a probe indicated that the root-tip cells having more than a 14-chromosome plus chromosome fragment count were a result of chromosome breakage or gap formation in vitro (referred to as chromosome lesions) at 45S rDNA sites, and 86% of the cells exhibited chromosome breaks or gaps and all occurred at the sites of 45S rDNA in Lolium perenne L. cv. Player, as well as in L. multiflorum Lam. cv. Top One. Chromatin depletion or decondensation occurred at various locations within the 45S rDNA regions, suggesting heterogeneity of lesions of 45S rDNA sites with respect to their position within the rDNA region. CONCLUSIONS: The chromosome lesions observed in this study are very similar cytologically to that of fragile sites observed in human chromosomes, and thus we conclude that the high frequency of chromosome lesions in vitro in Lolium species is the result of the expression of 45S rDNA fragile sites. Possible causes for the spontaneous expression of fragile sites and their potential biological significance are discussed
Single-nanoparticle phase transitions visualized by four-dimensional electron microscopy
The advancement of techniques that can probe the behaviour of individual nanoscopic objects is of paramount importance
in various disciplines, including photonics and electronics. As it provides images with a spatiotemporal resolution,
four-dimensional electron microscopy, in principle, should enable the visualization of single-nanoparticle structural
dynamics in real and reciprocal space. Here, we demonstrate the selectivity and sensitivity of the technique by visualizing
the spin crossover dynamics of single, isolated metalâorganic framework nanocrystals. By introducing a small aperture in
the microscope, it was possible to follow the phase transition and the associated structural dynamics within a single
particle. Its behaviour was observed to be distinct from that imaged by averaging over ensembles of heterogeneous
nanoparticles. The approach reported here has potential applications in other nanosystems and those that undergo
(bio)chemical transformations
Lipids modulate the conformational dynamics of a secondary multidrug transporter
Direct interactions with lipids have emerged as key determinants of the folding, structure and function of membrane proteins, but an understanding of how lipids modulate protein dynamics is still lacking. Here, we systematically explored the effects of lipids on the conformational dynamics of the proton-powered multidrug transporter LmrP from Lactococcus lactis, using the pattern of distances between spin-label pairs previously shown to report on alternating access of the protein. We uncovered, at the molecular level, how the lipid headgroups shape the conformational-energy landscape of the transporter. The model emerging from our data suggests a direct interaction between lipid headgroups and a conserved motif of charged residues that control the conformational equilibrium through an interplay of electrostatic interactions within the protein. Together, our data lay the foundation for a comprehensive model of secondary multidrug transport in lipid bilayers
DNA breaks at fragile sites generate oncogenic RET/PTC rearrangements in human thyroid cells
Human chromosomal fragile sites are regions of the
genome that are prone to DNA breakage, and are
classified as common or rare, depending on their frequency
in the population. Common fragile sites frequently
coincide with the location of genes involved in carcinogenic
chromosomal translocations, suggesting their role in
cancer formation. However, there has been no direct
evidence linking breakage at fragile sites to the formation
of a cancer-specific translocation. Here, we studied the
involvement of fragile sites in the formation of RET/PTC
rearrangements, which are frequently found in papillary
thyroid carcinoma (PTC). These rearrangements are
commonly associated with radiation exposure; however,
most of the tumors found in adults are not linked to
radiation. In this study, we provide structural and
biochemical evidence that the RET, CCDC6 and NCOA4
genes participating in two major types of RET/PTC
rearrangements, are located in common fragile sites
FRA10C and FRA10G, and undergo DNA breakage
after exposure to fragile site-inducing chemicals. Moreover,
exposure of human thyroid cells to these chemicals
results in the formation of cancer-specific RET/PTC
rearrangements. These results provide the direct evidence
for the involvement of chromosomal fragile sites in the
generation of cancer-specific rearrangements in human cell
Glancing through the debris disk: Photometric analysis of DE Boo with CHEOPS
DE Boo is a unique system, with an edge-on view through the debris disk around the star. The disk, which is analogous to the Kuiper belt in the Solar System, was reported to extend from 74 to 84 AU from the central star. The high photometric precision of the Characterising Exoplanet Satellite (CHEOPS) provided an exceptional opportunity to observe small variations in the light curve due to transiting material in the disk. This is a unique chance to investigate processes in the debris disk. Photometric observations of DE Boo of a total of four days were carried out with CHEOPS. Photometric variations due to spots on the stellar surface were subtracted from the light curves by applying a two-spot model and a fourth-order polynomial. The photometric observations were accompanied by spectroscopic measurements with the 1m RCC telescope at Piszk\'estet\H{o} and with the SOPHIE spectrograph in order to refine the astrophysical parameters of DE Boo. We present a detailed analysis of the photometric observation of DE Boo. We report the presence of nonperiodic transient features in the residual light curves with a transit duration of 0.3-0.8 days. We calculated the maximum distance of the material responsible for these variations to be 2.47 AU from the central star, much closer than most of the mass of the debris disk. Furthermore, we report the first observation of flaring events in this system. We interpreted the transient features as the result of scattering in an inner debris disk around DE Boo. The processes responsible for these variations were investigated in the context of interactions between planetesimals in the system
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