58 research outputs found
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
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
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
Twisting of graphene nanoribbons partially located on flat substrates
The molecular dynamics simulation of longitudinal twisting of graphene nanoribbons hanging from the edge of a flat substrate formed by the surface of a hexagonal boron nitride crystal has been performed. It has been shown that rotation of the free end of a nanoribbon causes twisting of the suspended region accompanied by monotonous sliding of the nanoribbon over the substrate. At the beginning, a regular screw-like shape is formed in the suspended section, next a super-twisted section emerges inside it, further growth of which occurs due to pulling of the nanoribbon from the substrate. After separation from the substrate, the twisted nanoribbon folds into a roll, so that further twisting results only in free rotation of the roll
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