Assembling nanostructures from DNA using a composite nanotweezers with a shape memory effect

The article demonstrates a technique for fabricating a structure with the inclusion of suspended DNA threads and manipulating them using composite nanotweezers with shape memory effect. This technique could be suitable for stretching of nanothin DNA-like conductive threads and for measuring their electrical conductivity, including the I-V characteristic directly in the electron microscope chamber, where the nanotweezers provide a two-sided clamping of the DNA tip, giving a stable nanocontact to the DNA bundle. Such contact, as a part of 1D nanostructure, is more reliable during manipulations with nanothreads than traditional measurements when a nanothread is touched by a thin needle, for example, in a scanning tunnel microscope.Comment: To be presented on IEEE 3M-NANO 201

Neutrino helicity asymmetries in leptogenesis

It is pointed out that the heavy singlet neutrinos characteristic of leptogenesis develop asymmetries in the abundances of the two helicity states as a result of the same mechanism that generates asymmetries in the standard lepton sector. Neutrinos and standard leptons interchange asymmetries in collisions with each other. It is shown that an appropriate quantum number, B-L', combining baryon, lepton and neutrino asymmetries, is not violated as fast as the standard B-L. This suppresses the washout effects relevant for the derivation of the final baryon asymmetry. One presents detailed calculations for the period of neutrino thermal production in the framework of the singlet seesaw mechanism.Comment: 11 pages, 1 figure, revtex, matches PRD versio

Nanosilver in Biomedicine: Advantages and Restrictions

Nanosilver (in a range 1–100 nm) binds with thyol-, amino- and carboxy-groups of aminoacid residues of proteins and nucleic acids, thus providing inactivation of pathogenic multidrug-resistant microorganisms. Besides antibacterial, antiviral, antifungal and anti-cancer properties Ag-based nanomaterials possess anti-inflammatory, anti-angiogenesis and antiplatelet features. Drug efficacy depends on their stability, toxicity and host immune response. Citrate coated Ag nanoparticles (NPs) remain stable colloid solutions in deionized water but not in the presence of ions due to replacement of Ag+ by electrolyte ions, potential formation of insoluble AgCl, subsequent catalyzed oxidative corrosion of Ag and further dissolution of surface layer of Ag2O. Protein shells protect core of AgNPs from oxidation, dissolution, aggregation and provide specific interactions with ligands. These nanoconjugates can be used for immunoassays and diagnostics but the sensitivity threshold does not exceed 10 pg Cytotoxicity of AgNPs conjugated with proteins is associated with the rate of intracellular Ag+ release, a ‘Trojan horse’ effect, and exceeds one of Ag+ because of endocytosis uptake of NPs but not ions. Relatively toxic nanosilver causes immunosuppression of the majority of cytokines with a few exceptions (IL-1β, G-CSF, MCP-1) whereas AgNO3 additionally activate TNFα and IL8 gene expression

Scanning Probe Microscopy of DNA on Mica and Graphite

Abstract. Method of modification of highly oriented pyrolytic graphite (HOPG) is proposed for deposition of biological objects especially DNA for scanning probe microscopy. Atomic force microscopy (AFM) images of DNA on HOPG are compared with those on conventional support -mica. The advantages of HOPG as a substrate for DNA for using in STM imaging and DNA mapping are discussed

Properties of an aqueous solution of ionic liquid [Emim][Cl] at standard atmospheric pressure

The density, viscosity, electric conductivity, volumetric thermal expansion coefficient, melting point, and refractive index of an aqueous solution of the [Emim][Cl] ionic liquid are measured over wide ranges of temperature and concentrations at standard atmospheric pressure. Analytical dependences of the investigated properties on the concentration and temperature are suggested

Ti2NiCu Based Composite Nanotweezers with a Shape Memory Effect and its Use for DNA Bunches 3D Manipulation

The DNA molecules were controllable deposited on graphene and thin graphite films and visualized using AFM. The mechanical micro- and nanotools, such as nanotweezers with shape memory effect controlled by heating were designed and tested. A technique for fabricating a structure with the inclusion of suspended DNA threads and manipulating those using composite nanotweezers with shape memory effect was suggested.Comment: arXiv admin note: text overlap with arXiv:1811.0294

Force spectroscopy of barnase-barstar single molecule interaction

Results of the single molecule force spectroscopy study of specific interactions between ribonuclease barnase and its inhibitor barstar are presented. Experimental data obtained for the force loading rate ranging 2-70 nN/s are well approximated by a single straight line, from which the dissociation barrier of the width of 0.12 nm and height of 0.75-0.85X10(-19) J can be inferred. The measured value of specific interaction does not depend on the NaCl concentration. This apparently contradicts the well-known dependence of the binding energy of this pair on the salt concentration, but such a "contradiction" is explained by the insensitivity of the force spectroscopy data to the relatively long-range electrostatic interaction. The latter essentially contributes to the value of barnase-barstar binding energy revealed by biochemical measurements, and it is exactly this electrostatic interaction which is influenced by the salt concentration. Copyright (C) 2010 John Wiley & Sons, Ltd

Оценка ожидаемой надежности прикладных программных средств для компьютерных информационных систем

The reliability of computer-based information systems is largely determined by the reliability of the developed application software. The failure rate of its computer program is considered as an indicator of the reliability of the application software. To determine the expected reliability of the application software planned for the development (until writing the code of a program), the model is proposed that uses some parameters of the future computer program, data on the influence of various factors on its reliability, and further testing of the program. The model takes into account the field of software application and computer processor performance. The process of model parameters obtaining is analyzed., It is possible by use of proposed model to determine the predicted failure rate of the planned application computer program, and then the reliability of the computer-based information system as a whole. If necessary, the measures can be developed to ensure the required level of reliability of the computer-based information system.Надежность компьютерной информационной системы во многом определяется надежностью разрабатываемого прикладного программного средства. В качестве показателя надежности прикладного программного средства рассматривается интенсивность отказов его компьютерной программы. Для определения ожидаемой надежности прикладного программного средства, планируемого к разработке (до написания кода компьютерной программы), предлагается модель, в которой используются некоторые параметры будущей компьютерной программы, данные о влиянии на ее надежность различных факторов и предполагаемое в дальнейшем тестирование компьютерной программы. Модель учитывает отрасль применения программного средства и быстродействие процессора компьютера. Анализируется процесс получения параметров модели. С помощью предложенной модели можно определить прогнозную интенсивность отказов планируемой к разработке прикладной компьютерной программы, а далее и надежность компьютерной информационной системы в целом. При необходимости могут быть разработаны организационно-технические мероприятия по обеспечению требуемого уровня надежности компьютерной информационной системы

A fluorescent microspheres-based microfluidic test system for the detection of immunoglobulin G to SARS-CoV-2

Background: The pandemic of the new coronavirus infection, COVID-19, is currently ongoing in the world. Over the years, the pathogen, SARS-CoV-2, has undergone a series of mutational genome changes, which has led to the spread of various genetic variants of the virus. Meanwhile, the methods used to diagnose SARS-CoV-2, to establish the disease stage and to assess the immunity, are nonspecific to SARS-CoV-2 variants and time-consumable. Thus, the development of new methods for diagnosing COVID-19, as well as their implementation in practice, is currently an important direction. In particular, application of systems based on chemically modified fluorescent microspheres (with a multiplex assay for target protein molecules) opens great opportunities. Aim: development of a microfluidic diagnostic test system based on fluorescent microspheres for the specific detection of immunoglobulins G (IgG) to SARS-CoV-2. Methods: A collection of human serum samples was characterized using enzyme-linked immunosorbent assay (ELISA) and commercially available reagent kits. IgG to SARS-CoV-2 in the human serum were detected by the developed immunofluorescent method using microspheres containing the chemically immobilized RBD fragment of the SARS-CoV-2 (Kappa variant) viral S-protein. Results: The level of IgG in the blood serum of recovered volunteers was 9-300 times higher than that in apparently healthy volunteers, according to ELISA (p0.001). Conjugates of fluorescent microspheres with the RBD-fragment of the S-protein, capable of specifically binding IgG from the blood serum, have been obtained. The immune complexes formation was confirmed by the fluorescence microscopy data; the fluorescence intensity of secondary antibodies in the immune complexes formed on the surface of microspheres was proportional to the content of IgG (r 0.963). The test system had a good predictive value (AUC 70.3%). Conclusion: A test system has been developed, based on fluorescent microspheres containing the immobilized RBD fragment of the SARS-CoV-2 S-protein, for the immunofluorescent detection of IgG in the human blood serum. When testing the system on samples with different levels of IgG to SARS-CoV-2, its prognostic value was shown. The obtained results allow us to present the test system as a method to assess the level of immunoglobulins to SARS-CoV-2 in the human blood serum for the implementation in clinical practice. The test system can also be integrated into various microfluidic systems to create chips and devices for the point-of-care diagnostics