Cells are constantly challenged by DNA damage and protect their genome integrity by activation of an evolutionary conserved DNA damage response pathway (DDR). A central core of DDR is composed of a spatiotemporally ordered net of post-translational modifications, among which protein phosphorylation plays a major role. Activation of checkpoint kinases ATM/ATR and Chk1/2 leads to a temporal arrest in cell cycle progression (checkpoint) and allows time for DNA repair. Following DNA repair, cells re-enter the cell cycle by checkpoint recovery. Wip1 phosphatase (also called PPM1D) dephosphorylates multiple proteins involved in DDR and is essential for timely termination of the DDR. Here we have investigated how Wip1 is regulated in the context of the cell cycle. We found that Wip1 activity is downregulated by several mechanisms during mitosis. Wip1 protein abundance increases from G(1) phase to G(2) and declines in mitosis. Decreased abundance of Wip1 during mitosis is caused by proteasomal degradation. In addition, Wip1 is phosphorylated at multiple residues during mitosis, and this leads to inhibition of its enzymatic activity. Importantly, ectopic expression of Wip1 reduced γH2AX staining in mitotic cells and decreased the number of 53BP1 nuclear bodies in G(1) cells. We propose that the combined decrease and inhibition of Wip1 in mitosis decreases the threshold necessary for DDR activation and enables cells to react adequately even to modest levels of DNA damage encountered during unperturbed mitotic progression.

• Klíčová slova
• DNA damage response, Wip1 phosphatase, cell cycle, mitotic progression, γH2AX,
• MeSH
• DNA primery genetika   MeSH
• fluorescenční protilátková technika MeSH
• fosforylace MeSH
• hmotnostní spektrometrie MeSH
• kontrolní body M fáze buněčného cyklu fyziologie   MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• lidé MeSH
• malá interferující RNA genetika   MeSH
• mitóza fyziologie   MeSH
• nádorové buněčné linie MeSH
• poškození DNA * MeSH
• proteinfosfatasa 2C MeSH
• proteinfosfatasy metabolismus   MeSH
• regulace genové exprese fyziologie   MeSH
• signální transdukce fyziologie   MeSH
• transfekce MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA primery MeSH
• malá interferující RNA MeSH
• PPM1D protein, human MeSH Prohlížeč
• proteinfosfatasa 2C MeSH
• proteinfosfatasy MeSH

Xray free-electron lasers (XFELs) enable experiments that would have been impractical or impossible at conventional X-ray laser facilities. Indeed, more XFEL facilities are being built and planned, with their aim to deliver larger pulse energies and higher peak brilliance. While seeking to increase the pulse power, it is quintessential to consider the maximum pulse fluence that a grazing-incidence FEL mirror can withstand. To address this issue, several studies were conducted on grazing-incidence damage by soft X-ray FEL pulses at the European XFEL facility. Boron carbide (B4C) coatings on polished silicon substrate were investigated using 1 keV photon energy, similar to the X-ray mirrors currently installed at the soft X-ray beamlines (SASE3). The purpose of this study is to compare the damage threshold of B4C and Si to determine the advantages, tolerance and limits of using B4C coatings.

• Klíčová slova
• B4C coating, X-ray mirrors, XFEL, damage threshold, single-shot damage threshold,
• Publikační typ
• časopisecké články MeSH

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface.

• Klíčová slova
• EUV optics, FELs, free-electron laser induced damage, thin films,
• Publikační typ
• časopisecké články MeSH

The electronic structure and linear and nonlinear optical susceptibility dispersions of lithium borate Li3B5O8(OH)2 are comprehensively investigated. The investigation is achieved on Li3B5O8(OH)2 in the form of single crystals, taking into account the influence of the packing of the structural units on the linear and nonlinear optical susceptibility dispersion. The calculations highlight that the BO3 structural unit packing is the main source of the large birefringence in Li3B5O8(OH)2 due to the high anisotropic electron distribution, and, hence, it affects the macroscopic second harmonic generation (SHG) coefficients. This work provides a new path for the design of UV-NLO materials with high SHG efficiencies and short cutoff edges by introducing an alkali metal into borates. The large SHG is due to hyperpolarizability formed by co-parallel BO3 triangle groups. The absorption edge of Li3B5O8(OH)2 occurs at λ = 190 nm and the optical band gap is estimated to be 6.52 eV, which is in good agreement with the experimental data (6.526 eV). The energy gap value confirms that Li3B5O8(OH)2 exhibits an exceptional laser damage threshold and is expected to produce coherent radiation in the deep-ultraviolet (DUV) region. The obtained value of SHG at λ = 1064 nm is about 1.5 times that of the well-known NLO crystal KH2PO4 (KDP) at λ = 1064 nm and 3.5 times that of KDP at λ = 190 nm, which is transparent down to the DUV region. Thus, one can conclude that the combination of an alkali metal with borates leads to the generation of promising DUV-NLO crystals. This work is aimed at qualitative and quantitative investigation to report a reliable SHG value and provide details of the NLO tensor for bulk Li3B5O8(OH)2 single crystals.

• Publikační typ
• časopisecké články MeSH

Alcobiosis, the symbiosis of algae and corticioid fungi, frequently occurs on bark and wood. Algae form a layer in or below fungal basidiomata reminiscent of the photobiont layer in lichens. Identities of algal and fungal partners were confirmed by DNA barcoding. Algal activity was examined using gas exchange and chlorophyll fluorescence techniques. Carbon transfer from algae to fungi was detected as 13C, assimilated by algae, transferred to the fungal polyol. Nine fungal partners scattered across Agaricomycetes are associated with three algae from Trebouxiophycae: Coccomyxa sp. with seven fungal species on damp wood, Desmococcus olivaceus and Tritostichococcus coniocybes, both with a single species on bark and rain-sheltered wood, respectively. The fungal partner does not cause any obvious harm to the algae. Algae enclosed in fungal tissue exhibited a substantial CO2 uptake, but carbon transfer to fungal tissues was only detected in the Lyomyces-Desmococcus alcobiosis where some algal cells are tightly enclosed by hyphae in goniocyst-like structures. Unlike lichen mycobionts, fungi in alcobioses are not nutritionally dependent on the algal partner as all of them can live without algae. We consider alcobioses to be symbioses in various stages of co-evolution, but still quite different from true lichens.

• MeSH
• alarminy MeSH
• biologický transport MeSH
• ekzém * MeSH
• hyfy MeSH
• keratóza * MeSH
• lišejníky * MeSH
• uhlík MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• alarminy MeSH
• uhlík MeSH

Homocysteinemia increased significantly after a methionine load of 50 mg/kg in patients with peripheral artery occlusive disease but this load was insufficient to increase circulating endothelial cell count as a marker of endothelial damage. Only after an increased load of 100 mg/kg methionine circulating endothelial cells also increased markedly confirming the results of a previous experimental study. These data indicate a threshold concentration of homocysteine in blood necessary to induce endothelial lesions.

• MeSH
• arteriální okluzní nemoci metabolismus   patologie   MeSH
• cévní endotel účinky léků   zranění   patologie   MeSH
• homocystein krev   MeSH
• krevní buňky patologie   MeSH
• krevní obraz MeSH
• lidé středního věku MeSH
• lidé MeSH
• methionin aplikace a dávkování   MeSH
• onemocnění periferních cév metabolismus   patologie   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• homocystein MeSH
• methionin MeSH

Mitochondrial ATP synthase is responsible for production of the majority of cellular ATP. Disorders of ATP synthase in humans can be caused by numerous mutations in both structural subunits and specific assembly factors. They are associated with variable pathogenicity and clinical phenotypes ranging from mild to the most severe mitochondrial diseases. To shed light on primary/pivotal functional consequences of ATP synthase deficiency, we explored human HEK 293 cells with a varying content of fully assembled ATP synthase, selectively downregulated to 15-80% of controls by the knockdown of F1 subunits γ, δ and ε. Examination of cellular respiration and glycolytic flux revealed that enhanced glycolysis compensates for insufficient mitochondrial ATP production while reduced dissipation of mitochondrial membrane potential leads to elevated ROS production. Both insufficient energy provision and increased oxidative stress contribute to the resulting pathological phenotype. The threshold for manifestation of the ATP synthase defect and subsequent metabolic remodelling equals to 10-30% of residual ATP synthase activity. The metabolic adaptations are not able to sustain proliferation in a galactose medium, although sufficient under glucose-rich conditions. As metabolic alterations occur when the content of ATP synthase drops below 30%, some milder ATP synthase defects may not necessarily manifest with a mitochondrial disease phenotype, as long as the threshold level is not exceeded.

• Klíčová slova
• ATP synthase, Deficiency, Oxidative phosphorylation, Reactive oxygen species, Threshold effect,
• MeSH
• buněčné klony MeSH
• genový knockdown MeSH
• glykolýza MeSH
• HEK293 buňky MeSH
• inhibiční koncentrace 50 MeSH
• lidé MeSH
• mitochondriální protonové ATPasy nedostatek   metabolismus   MeSH
• oxidační stres MeSH
• termodynamika MeSH
• viabilita buněk MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• mitochondriální protonové ATPasy MeSH

Cadmium sulfide is a valuable material for solar cells, photovoltaic, and radiation detectors. It is thus important to evaluate the material damage mechanisms and damage threshold in response to irradiation. Here, we simulate the ultrafast XUV/X-ray irradiation of CdS with the combined model, XTANT-3. It accounts for nonequilibrium electronic and atomic dynamics, nonadiabatic coupling between the two systems, nonthermal melting and bond breaking due to electronic excitation. We find that the two phases of CdS, zinc blende and wurtzite, demonstrate very close damage threshold dose of ∼0.4-0.5 eV per atom. The damage is mainly thermal, whereas with increase of the dose, nonthermal effects begin to dominate leading to nonthermal melting. The transient disordered state is a high-density liquid, which may be semiconducting or metallic depending on the dose. Later recrystallization may recover the material back to the crystalline phase, or at high doses create an amorphous phase with variable bandgap. The revealed effects may potentially allow for controllable tuning of the band gap via laser irradiation of CdS.

• Publikační typ
• časopisecké články MeSH

Although polymers are widely used in laser-irradiation research, their microscopic response to high-intensity ultrafast XUV and X-ray irradiation is still largely unknown. Here, we comparatively study a homologous series of alkenes. The XTANT-3 hybrid simulation toolkit is used to determine their damage kinetics and irradiation threshold doses. The code simultaneously models the nonequilibrium electron kinetics, the energy transfer between electrons and atoms via nonadiabatic electron-ion (electron-phonon) coupling, nonthermal modification of the interatomic potential due to electronic excitation, and the ensuing atomic response and damage formation. It is shown that the lowest damage threshold is associated with local defect creation, such as dehydrogenation, various group detachments from the backbone, or polymer strand cross-linking. At higher doses, the disintegration of the molecules leads to a transient metallic liquid state: a nonequilibrium superionic state outside of the material phase diagram. We identify nonthermal effects as the leading mechanism of damage, whereas the thermal (nonadiabatic electron-ion coupling) channel influences the kinetics only slightly in the case of femtosecond-pulse irradiation. Despite the notably different properties of the studied alkene polymers, the ultrafast-X-ray damage threshold doses are found to be very close to ∼0.05 eV/atom in all three materials: polyethylene, polypropylene, and polybutylene.

• Publikační typ
• časopisecké články MeSH

• MeSH
• audiometrie * MeSH
• lidé MeSH
• Menierova nemoc diagnóza   MeSH
• nervus cochlearis MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH