The spatial organization of chromosomes is involved in regulating the majority of intranuclear processes in higher eukaryotes, including gene expression. Drosophila was used as a model to discover ...many transcription factors whose homologs play a key role in regulation of gene expression in mammals. According to modern views, a cohesin complex mostly determines the architecture of mammalian chromosomes by forming chromatin loops on anchors created by the CTCF DNA-binding architectural protein. The role of the cohesin complex in chromosome architecture is poorly understood in Drosophila, and CTCF is merely one of many Drosophila architectural proteins with a proven potential to organize specific long-range interactions between regulatory elements in the genome. The review compares the mechanisms responsible for long-range interactions and chromosome architecture between mammals and Drosophila.
The heat absorbed by the heat transfer fluid for cooling a concentrated photovoltaic thermal (CPVT) solar collector can be used for purposes such as residential heating and cooking. Because of the ...combined production of heat and power, these systems are proposed for individual or commercial use in rural areas. In this study, a hybrid system was proposed to increase the electrical efficiency of the system. Experiments were conducted in winter conditions. Two operational modes were compared, namely a CPVT system with HP (HP-CPVT) and without HP (CPVT). The evaporator of the heat pump was settled inside the triangular trough receiver. The effects of cooling the PV system with a heat pump in the bifacial CPVT system on the electrical and thermal energy efficiencies were investigated. The electricity and thermal energy efficiencies of the CPVT system were calculated as 12.54% and 38.37% in the HP-CPVT system, respectively, and 10.05% and 81.97% in the CPVT system, respectively. The electrical exergy efficiencies of the CPVT system with and without HP were 14.65% and 10.73%, respectively. The thermal exergy efficiencies of the CPVT system with and without HP were 82.47% and 85.63%, respectively. The thermal heat obtained from the HP-CPVT system can be used for heating needs. Thus, the bifacial HP-CPVT system was an example of the micro-CHP system.
Messenger RNA of animal cells has been discovered, and a method for its isolation in pure form has been developed. It was established that it has the same nucleotide composition as DNA (dRNA). ...The nuclear dRNA contains both the newly formed mRNA precursor, pre-mRNA, and the mature mRNA. Pre-mRNA has a significantly higher molecular weight than mRNA. The content of dRNA comprises from 1/3 to 1/2 of the entire nuclear RNA. The organization of dRNA-containing nuclear nucleoprotein complexes was disclosed: a long dRNA molecule is wound on the surface of a series of globular multiprotein particles (informofers), which are connected by RNA bridges. One informofer has an RNA segment 700 nucleotides long. This previously unknown structure of nucleoproteins provides a sharp reduction in the linear dimensions of RNA while maintaining its accessibility to various protein factors. During further research, mobile genetic elements of animals were discovered. It has been established that almost all moderate repeats of the genome, that is, about 10% of the latter, are mobile elements of different sizes. Two main types of mobile elements in Drosophila and mice have been identified and characterized.
The emergence of whole-genome assays has initiated numerous genome-wide studies of transcription factor localizations at genomic regulatory elements (enhancers, promoters, silencers, and insulators), ...as well as facilitated the uncovering of some of the key principles of chromosomal organization. However, the proteins involved in the formation and maintenance of the chromosomal architecture and the organization of regulatory domains remain insufficiently studied. This review attempts to collate the available data on the abundant but still poorly understood family of proteins with clusters of the C2H2 zinc finger domains. One of the best known proteins of this family is a well conserved protein known as CTCF, which plays a key role in the establishment of the chromosomal architecture in vertebrates. The distinctive features of C2H2 zinc finger proteins include strong and specific binding to a long and unique DNA recognition target sequence and rapid expansion within various animal taxa during evolution. The reviewed data support a proposed model according to which many of the C2H2 proteins have functions that are similar to those of the CTCF in the organization of the chromatin architecture.
We describe how reactivity can be controlled in the solid state using molecules and self-assembled metal−organic complexes as templates. Being able to control reactivity in the solid state bears ...relevance to synthetic chemistry and materials science. The former offers a promise to synthesize molecules that may be impossible to realize from the liquid phase while also taking advantage of the benefits of conducting highly stereocontrolled reactions in a solvent-free environment (i.e., green chemistry). The latter provides an opportunity to modify bulk physical properties of solids (e.g., optical properties) through changes to molecular structure that result from a solid-state reaction. Reactions in the solid state have been difficult to control owing to frustrating effects of molecular close packing. The high degree of order provided by the solid state also means that the templates can be developed to determine how principles of supramolecular chemistry can be generally employed to form covalent bonds. The paradigm of synthetic chemistry employed by Nature is based on integrating noncovalent and covalent bonds. The templates assemble olefins via either hydrogen bond or coordination-driven self-assembly for intermolecular 2 + 2 photodimerizations. The olefins are assembled within discrete, or finite, self-assembled complexes, which effectively decouples chemical reactivity from effects of crystal packing. The control of the solid-state assembly process affords the supramolecular construction of targets in the form of cyclophanes and ladderanes. The targets form stereospecifically, in quantitative yield, and in gram amounts. Both 3- and 5-ladderanes have been synthesized. The ladderanes are comparable to natural ladderane lipids, which are a new and exciting class of natural products recently discovered in anaerobic marine bacteria. The organic templates function as either hydrogen bond donors or hydrogen bond acceptors. The donors and acceptors generate cyclobutanes lined with pyridyl and carboxylic acid groups, respectively. The metal−organic templates are based on Zn(II) and Ag(I) ions. The reactivity involving Zn(II) ions is shown to affect optical properties in the form of solid-state fluorescence. The solids based on both the organic and metal−organic templates undergo rare single-crystal-to-single-crystal reactions. We also demonstrate how the cyclobutanes obtained from this method can be applied as novel polytopic ligands of metallosupramolecular assemblies (e.g., self-assembled capsules) and materials (e.g., metal−organic frameworks). Sonochemistry is also used to generate nanostructured single crystals of the multicomponent solids or cocrystals based on the organic templates. Collectively, our observations suggest that the organic solid state can be integrated into more mainstream settings of synthetic organic chemistry and be developed to construct functional crystalline solids.
Abstract
This paper presents procedures of processing and recognition of color images by means of artificial intelligence and computer aided training. Two stages of processing have been applied with ...regard to extraction of features. Processing involves conversion of RGB images in grayscale and binary; and conversion of RGB, grayscale and binary into index formats. Spectral analysis is also applied in here with Fourier’s algorithm for fast conversion concerning indicated graphic formats and segmentation of the real and imaginary complex parts. Activities related with training, assessment and synthesis of feed-forward neural networks and probabilistic neural networks, based on Accuracy and Mean-Squared Error analysis. Special emphasis is made on a method for computer aided training k-nearest neighbors with Euclidean, Euclidean squared, Cityblock and Chebychev metric distances in relation to Cross-validation accuracy value. Some positive indications have been achieved in recognition of assigned graphic images by means of the employed mathematical apparatus.
Informative numerical representations of amino acid residues are essential for successful in silico modeling or establishing the structure-activity relationships of proteins. A straightforward ...approach is adopted here for representing more than 500 amino acid indices from the AAindex database by a set of uncorrelated scales, satisfying the varimax criterion. Different measures are considered in order to demonstrate the improved interpretability of the current scales as compared to previously published ones. Performance is also addressed in a classification problem of G-protein coupled receptors, and is found to be similar or higher than the performance achieved by six other scale sets. Finally, a unique correspondence between numerical indices and mutation matrices is derived and discussed in light of the evolutionary conservation of amino acid properties. Conclusions from this study highlight the discord between ease of interpretation of amino acid scales and their relevance to protein structure conservation, as well as general considerations for designing custom scale sets.
A
bstract
This paper presents a detailed characterization of the positron beam delivered by the Beam Test Facility at Laboratori Nazionali of Frascati to the PADME experiment during Run III, which ...took place from October to December 2022. It showcases the methodology used to measure the main beam parameters such as the position in space, the absolute momentum scale, the beam energy spread, and its intensity through a combination of data analysis and Monte Carlo simulations. The results achieved include an absolute precision in the momentum of the beam to within ~1–2 MeV
/c
, a relative beam energy spread below 0.25%, and an absolute precision in the intensity of the beam at the level of 2%.
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