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132 result(s) for "Novak, Josef"
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Insulator Material Deposited with Molybdenum Disulphide Prospective for Sensing Application
Two-dimensional molybdenum disulfide (MoS2) exhibits interesting properties for applications in micro and nano-electronics. The key point for sensing properties of a device is the quality of the material’s surface. In this study, MoS2 layers were deposited on polymers by pulsed laser deposition (PLD). This process was monitored by a mass quadrupole spectrometer to record the emissions of MoS2 and evaluate the amount of molybdenum and sulfur compounds generated. The changes in laser parameters during the PLD strongly affect the properties of the formed MoS2 film. The exploration of the composition and structure of the films was followed by Attenuated Total Reflectance–Fourier Transform Infrared (ATR-FTIR), Atomic Force Microscopy (AFM), and mass quadrupole spectrometer (MQS). The possible application of the fabricated composite as a sensor is preliminarily considered.
Topological stress triggers persistent DNA lesions in ribosomal DNA with ensuing formation of PML-nucleolar compartment
PML, a multifunctional protein, is crucial for forming PML-nuclear bodies involved in stress responses. Under specific conditions, PML associates with nucleolar caps formed after RNA polymerase I (RNAPI) inhibition, leading to PML-nucleolar associations (PNAs). This study investigates PNAs-inducing stimuli by exposing cells to various genotoxic stresses. We found that the most potent inducers of PNAs introduced topological stress and inhibited RNAPI. Doxorubicin, the most effective compound, induced double-strand breaks (DSBs) in the rDNA locus. PNAs co-localized with damaged rDNA, segregating it from active nucleoli. Cleaving the rDNA locus with I-PpoI confirmed rDNA damage as a genuine stimulus for PNAs. Inhibition of ATM, ATR kinases, and RAD51 reduced I-PpoI-induced PNAs, highlighting the importance of ATM/ATR-dependent nucleolar cap formation and homologous recombination (HR) in their triggering. I-PpoI-induced PNAs co-localized with rDNA DSBs positive for RPA32-pS33 but deficient in RAD51, indicating resected DNA unable to complete HR repair. Our findings suggest that PNAs form in response to persistent rDNA damage within the nucleolar cap, highlighting the interplay between PML/PNAs and rDNA alterations due to topological stress, RNAPI inhibition, and rDNA DSBs destined for HR. Cells with persistent PNAs undergo senescence, suggesting PNAs help avoid rDNA instability, with implications for tumorigenesis and aging.
Determination of ADP/ATP translocase isoform ratios in malignancy and cellular senescence
Cellular senescence has recently been recognized as a significant contributor to the poor prognosis of glioblastoma, one of the most aggressive brain tumors. Consequently, effectively eliminating senescent glioblastoma cells could benefit patients. Human ADP/ATP translocases (ANTs) play a role in oxidative phosphorylation in both normal and tumor cells. Previous research has shown that the sensitivity of senescent cells to mitochondria‐targeted senolytics depends on the level of ANT2. Here, we systematically mapped the transcript and protein levels of ANT isoforms in various types of senescence and glioblastoma tumorigenesis. We employed bioinformatics analysis, targeted mass spectrometry, RT‐PCR, immunoblotting, and assessment of cellular energy state to elucidate how individual ANT isoforms are expressed during the development of senescence in noncancerous and glioblastoma cells. We observed a consistent elevation of ANT1 protein levels across all tested senescence types, while ANT2 and ANT3 exhibited variable changes. Alterations in ANT protein isoform levels correlated with shifts in the cellular oxygen consumption rate. Our findings suggest that ANT isoforms are mutually interchangeable for oxidative phosphorylation and manipulating individual ANT isoforms could have potential for senolytic therapy. The individual functions of three isoforms exchanging ADP and ATP (ADP/ATP translocases; ANTs) on the mitochondrial membrane remain unclear. We developed a method for quantitatively differentiating highly similar human ANT1, ANT2, and ANT3 using parallel reaction monitoring. This method allowed us to assess changes in translocase levels during cellular senescence and correlate them with alterations in energy metabolism.
N-Terminal Domain of Nuclear IL-1α Shows Structural Similarity to the C-Terminal Domain of Snf1 and Binds to the HAT/Core Module of the SAGA Complex
Interleukin-1α (IL-1α) is a proinflammatory cytokine and a key player in host immune responses in higher eukaryotes. IL-1α has pleiotropic effects on a wide range of cell types, and it has been extensively studied for its ability to contribute to various autoimmune and inflammation-linked disorders, including rheumatoid arthritis, Alzheimer's disease, systemic sclerosis and cardiovascular disorders. Interestingly, a significant proportion of IL-1α is translocated to the cell nucleus, in which it interacts with histone acetyltransferase complexes. Despite the importance of IL-1α, little is known regarding its binding targets and functions in the nucleus. We took advantage of the histone acetyltransferase (HAT) complexes being evolutionarily conserved from yeast to humans and the yeast SAGA complex serving as an epitome of the eukaryotic HAT complexes. Using gene knock-out technique and co-immunoprecipitation of the IL-1α precursor with TAP-tagged subunits of the yeast HAT complexes, we mapped the IL-1α-binding site to the HAT/Core module of the SAGA complex. We also predicted the 3-D structure of the IL-1α N-terminal domain, and by employing structure similarity searches, we found a similar structure in the C-terminal regulatory region of the catalytic subunit of the AMP-activated/Snf1 protein kinases, which interact with HAT complexes both in mammals and yeast, respectively. This finding is further supported with the ability of the IL-1α precursor to partially rescue growth defects of snf1Δ yeast strains on media containing 3-Amino-1,2,4-triazole (3-AT), a competitive inhibitor of His3. Finally, the careful evaluation of our data together with other published data in the field allows us to hypothesize a new function for the ADA complex in SAGA complex assembly.
FEM Analysis of the Effect of Polarization on the Electromechanical Coupling Factor of Resonators with a Wrap-Around Electrode
The efficiency of electromechanical conversion in piezoelectric elements is assessed according to the magnitude of the electromechanical coupling coefficient. For power applications of piezoelectric elements, it is desirable that the efficiency of electrical to mechanical energy conversion be as high as possible. In case of resonators with electrodes incompletely covering their bases, an inhomogeneous electric field is generated, which results in inhomogeneous polarization of the resonator. The resonator will be polarized in some places either in a direction other than the desired one or not polarized at all. The degree of polarization of the resonator is one of the factors affecting the electromechanical coupling coefficient. The aim of this work is to analyze the magnitude of the electromechanical coupling coefficient of resonators with electrodes incompletely covering the bases and to compare the results with the electromechanical coupling coefficient of resonators with fully electroded bases. The physical description is given by the linear piezoelectric equations, the Gaussian equation for the electric field, and by Newton’s law of force. On this basis, a FEM model is developed and used to analyze the electromechanical coupling coefficient. The result of the calculation of the electromechanical coupling cofficient is that for resonators with a wrap-around electrode in studied shape and dimensions there will be a decrease in the electromechanical coupling coefficient compared to a fully electroded resonator of identical dimensions. The presented conclusions are compared with analytically and experimentaly achieved results.
FEM Analysis of Piezoelectric Resonator Polarization Process
The polarization of the piezoelectric resonator depends on the direction of the applied electric field. The direction of the applied electric field is determined by the shape of the resonator and the position of the electrodes. In case of resonators with electrodes incompletely covering their bases, an inhomogeneous electric field is generated, which results in an inhomogeneous polarization of the resonator. The resonator will be polarized in some places either in a direction other than the desired one or not polarized at all. The aim of this work is to analyze the polarization process on resonators with electrodes incompletely covering their bases. The physical description is given by the linear piezoelectric equations, the Gaussian equation for the description of the electric field and by Newton’s law of force. On this basis, a FEM model is developed and used to analyze the polarization process. The results of the calculation of the electric field vector distribution are presented. Finally, the areas are identified in which polarization in the desired direction is achieved in the resonator as well as the ones where no polarization occurs.
Electrical, photocatalytic, and sensory properties of graphene oxide and polyimide implanted with low- and medium-energy silver ions
Precise control of electrical conductivity, humidity sensitivity, and photocatalytic activity in polymeric and carbon-based materials is essential for advancing technologies in environmental sensing, flexible electronics, and photocatalytic systems. Conventional chemical modification methods often lack spatial precision, introduce impurities, and risk structural degradation. Ion implantation provides a controllable alternative for tuning surface properties at the nanoscale, enabling the targeted introduction of functional species without chemical reagents. This work investigates the effects of low-energy (20 keV) and medium-energy (1.5 MeV) Ag + ion implantation on the electrical, sensory, and photocatalytic properties of graphene oxide (GO) and polyimide (PI). Implantations were carried out with fluences ranging from 3.75 × 10 12 cm −2 to 1 × 10 16 cm −2 . Silver ions offer excellent electrical, catalytic, and plasmonic characteristics, making them ideal for multifunctional enhancement of GO and PI. Elemental and structural changes induced by implantation were analyzed using Rutherford backscattering spectroscopy, elastic recoil detection analysis, Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Surface morphology was assessed via atomic force microscopy. Electrical properties as a function of air humidity were evaluated using a two-point method, and photocatalytic activity was tested by monitoring the UV-induced decomposition of rhodamine B. The results demonstrate that ion implantation significantly reduces surface resistivity and enhances both the photocatalytic activity and humidity sensitivity of GO and PI. The most pronounced improvements occurred at higher fluences, where defect generation and partial deoxygenation contributed to optimal performance. Ion implantation thus represents an effective approach for tuning the multifunctional behavior of polymer systems.
Transcription apparatus of the yeast virus-like elements: Architecture, function, and evolutionary origin
Extrachromosomal hereditary elements such as organelles, viruses, and plasmids are important for the cell fitness and survival. Their transcription is dependent on host cellular RNA polymerase (RNAP) or intrinsic RNAP encoded by these elements. The yeast Kluyveromyces lactis contains linear cytoplasmic DNA virus-like elements (VLEs, also known as linear plasmids) that bear genes encoding putative non-canonical two-subunit RNAP. Here, we describe the architecture and identify the evolutionary origin of this transcription machinery. We show that the two RNAP subunits interact in vivo, and this complex interacts with another two VLE-encoded proteins, namely the mRNA capping enzyme and a putative helicase. RNAP, mRNA capping enzyme and the helicase also interact with VLE-specific DNA in vivo. Further, we identify a promoter sequence element that causes 5' mRNA polyadenylation of VLE-specific transcripts via RNAP slippage at the transcription initiation site, and structural elements that precede the termination sites. As a result, we present a first model of the yeast virus-like element transcription initiation and intrinsic termination. Finally, we demonstrate that VLE RNAP and its promoters display high similarity to poxviral RNAP and promoters of early poxviral genes, respectively, thereby pointing to their evolutionary origin.
Phonetisaurus: Exploring grapheme-to-phoneme conversion with joint n-gram models in the WFST framework
This paper provides an analysis of several practical issues related to the theory and implementation of Grapheme-to-Phoneme (G2P) conversion systems utilizing the Weighted Finite-State Transducer paradigm. The paper addresses issues related to system accuracy, training time and practical implementation. The focus is on joint n-gram models which have proven to provide an excellent trade-off between system accuracy and training complexity. The paper argues in favor of simple, productive approaches to G2P, which favor a balance between training time, accuracy and model complexity. The paper also introduces the first instance of using joint sequence RnnLMs directly for G2P conversion, and achieves new state-of-the-art performance via ensemble methods combining RnnLMs and n-gram based models. In addition to detailed descriptions of the approach, minor yet novel implementation solutions, and experimental results, the paper introduces Phonetisaurus, a fully-functional, flexible, open-source, BSD-licensed G2P conversion toolkit, which leverages the OpenFst library. The work is intended to be accessible to a broad range of readers.
Constitutive and ligand‐induced nuclear localization of oxytocin receptor
Oxytocin receptor (OTR) is a membrane protein known to mediate oxytocin (OT) effects, in both normal and neoplastic cells. We report here that human osteosarcoma (U2OS, MG63, OS15 and SaOS2), breast cancer (MCF7), and primary human fibroblastic cells (HFF) all exhibit OTR not only on the cell membrane, but also in the various nuclear compartments including the nucleolus. Both an OTR‐GFP fusion protein and the native OTR appear to be localized to the nucleus as detected by transfection and/or confocal immunofluorescence, respectively. Treatment with oxytocin causes internalization of OTR and the resulting vesicles accumulate in the vicinity of the nucleus and some of the perinuclear OTR enters the nucleus. Western blots indicate that OTR in the nucleus and on the plasma membrane are likely to be the same biochemical and immunological entities. It appears that OTR is first visible in the nucleoli and subsequently disperses within the nucleus into 4–20 spots while some of the OTR diffuses throughout the nucleoplasm.The behaviour and kinetics of OTR‐GFP and OTR are different, indicating interference by GFP in both OTR entrance into the nucleus and subsequent relocalization of OTR within the nucleus. There are important differences among the tested cells, such as the requirement of a ligand for transfer of OTR in nuclei. A constitutive internalization of OTR was found only in osteosarcoma cells, while the nuclear localization in all other tested cells was dependent on ligand binding. The amount of OTR‐positive material within and in the vicinity of the nucleus increased following a treatment with oxytocin in both constitutive and ligand‐dependent type of cells. The evidence of OTR compartmentalization at the cell nucleus (either ligand‐dependent or constitutive) in different cell types suggests still unknown biological functions of this protein or its ligand and adds this G‐protein‐coupled receptor to other heptahelical receptors displaying this atypical and unexpected nuclear localization.