The technique of AFM bending test of a suspended nanoobject has been improved.An analytical method has been created for calculating Young's and shear moduli of object's material based on data of such tests.In Timoshenko approximation, we consider problems of bending a beam one or both ends of which lie on elastic Winkler foundations.The obtained solutions are used to eliminate uncertainties in the calculation of elastic moduli that arise when the conditions of fixing an object (console or bridge) on the edges of a recess in the substrate are unknown.

We present the results of study the structure and composition of microcrystalline diamonds obtained by high-pressure high temperature sintering of detonation nanodiamond particles. Using optical detected magnetic resonance method, photoluminescence spectroscopy and Raman spectroscopy we found sintering of detonation nanodiamond significantly differ from initial detonation nanodiamonds and can be compared to high quality diamonds. Monocrystals of diamonds obtained by the method of oriented attachment have dimensions of up to tens of microns, possess the habitus of high-quality diamonds, and do not contain metal catalysts in the lattice structure. In those crystals, the presence of optically active nitrogen impurities in the crystal lattice is observed. In particular, there is a bright nitrogen-vacancy defects. They are characterized by optical detected magnetic resonance method, which shows that spin properties of the obtained single crystals correspond to high-quality natural diamonds and surpass synthetic diamonds obtained from graphite in the presence of metal catalysts, followed by irradiation and annealing to obtain nitrogen-vacancy defects optical defects in the diamond lattice. The presence of nitrogen vacancy defects and the high-quality of the crystal structure of sintering of detonation nanodiamond allows us to consider them as potential candidates in quantum magnetometry. For this purpose, the possibility of a simple way to improve the AFM probe by fixing a microcrystalline sintering of detonation nanodiamond particle on its tip is demonstrated.

Background: The gene expression differs in the nuclei of normal and malignant mammalian cells, and transcription is a critical initial step, which defines the difference. The mechanical properties of transcriptionally active chromatin are still poorly understood. Recently we have probed transcriptionally active chromatin of the nuclei subjected to mechanical stress, by Atomic Force Microscopy (AFM) [1]. Nonetheless, a systematic study of the phenomenon is needed. Methods: Nuclei were deformed and studied by AFM. Non-deformed nuclei were studied by fluorescence confocal microscopy. Their transcriptional activity was studied by RNA electrophoresis. Results: The malignant nuclei under the study were stable to deformation and assembled of 100-300 nm beadslike units, while normal cell nuclei were prone to deformation. The difference in stability to deformation of the nuclei correlated with DNA supercoiling, and transcription-depended units were responsive to supercoils breakage. The inhibitors of the topoisomerases I and II disrupted supercoiling and made the malignant nucleus prone to deformation. Cell nuclei treatment with histone deacetylase inhibitors (HDACIs) preserved the mechanical stability of deformed malignant nuclei and, at the same time, made it possible to observe chromatin decondensation up to 20-60 nm units. The AFM results were supplemented with confocal microscopy and RNA electrophoresis data. Conclusions: Self-assembly of transcriptionally active chromatin and its decondensation, driven by DNA supercoiling-dependent rigidity, was visualized by AFM in the mechanically deformed nuclei. General significance: We demonstrated that supercoiled DNA defines the transcription mechanics, and hypothesized the nuclear mechanics in vivo should depend on the chromatin architecture.

Here, we investigate an influence of Fe3+ content on the mechanical behavior of Mg3Si2O5(OH)4 synthetic phyllosilicate nanoscrolls with chrysotile structure during the bending tests carried out by atomic force microscopy. The developed approach to the microscopy data treatment allowed us to consider fixing conditions, elasticity of the foundation, and shear strain contributions to the observed Young’s modulus value. Doping by 6 at.% of Fe3+ decreased the Young’s modulus from 238 down to 150 GPa. The applied density-functional theory calculations confirmed the same trend for the most energy preferable types of Mg2+ and Si4+ substitutons by Fe3+. Despite major part of the experimental data has been satisfactory explained within the shear strain contribution assumption, doping by Fe3+ gives rise to nanoscrolls with anomalous Young’s modulus value (600±200 GPa). Potential reasons of the effect are considered.

Basal-faceted sapphire ribbons grown using the Stepanov-LaBelle technology have a low density of surface steps. We present our results on a study of steps on the surface of a ribbon, misoriented relative to the singular face (0001) by several arc minutes. The ribbon has been characterized by means of in-line phase contrast imaging technique at Pohang Light Source, South Korea. It was shown for the first time that a step height of about 1 mu m can be determined directly from an image. The step height obtained using the phase contrast method was confirmed by atomic force microscopy measurements. We have found that the experimental contrast matches the theoretical simulations only if the calculated intensity profile has been convolved with a Gaussian function. The full width at half maximum of the Gaussian was independently got from previous measurements. We have obtained an analytical solution in the case of theoretical fully coherent phase contrast image. The inverse problem is easy to solve, since there is a direct proportionality between the contrast and the step height.

Consoles and bridges of MgNi2Si2O5(OH)4 nanoscrolls were tested for bending in atomic force microscope. Using test data, we analyze how the consoles or bridges were fixed, and took this information into account when calculating the Young’s modulus of the nanoscrolls. The results on the consoles are in good agreement with the results on the bridges when modeling the latter as three-span beams, and the former as beams on an elastic foundation with a suspended console.

It has been generally accepted that heterochromatin is represented by a regular, dense and closed structure, while euchromatin is open and sparse. Recent evidence indicates that chromatin is comprised of irregular nucleosome clutches compacted within the nucleus. Transcriptional events transform the chromatin architecture, resulting in appearance of 100-300 nm nucleosomal aggregates. Meanwhile, the current paradigm of chromatin architecture is largely fragmented. In this communication, we unraveled chromatin ultrastructure of normal and malignant cell nuclei through mechanical deformation of the nuclei and Atomic Force Microscopy (AFM) analysis of the resulting landscape. In human skin fibroblasts cell nuclei, nanodomains of about 16.5-33.5 nm were revealed. Hierarchical folding of the chromatin of normal nuclei was observed: the nanodomains formed irregular fiber-like structures that coalesced into the macroscale chromatin compartments. In fibrosarcoma cell nuclei DNA supercoiling domains (SDs) of about 66.3-113.0 nm, uniformly distributed within the nuclei, were revealed. Transformation of the morphology of the condensed chromatin domains through up- and downregulation of supercoiling was demonstrated.

Conductive electrochemically active metallopolymers are outstanding materials for energy storage and conversion, electrocatalysis, electroanalysis, and other applications. The hybrid inorganic–organic nature of these materials ensures their rich chemistry and offers wide opportunities for fine-tuning their functional properties. The electrochemical modulation of the nanomechanical properties of metallopolymers is rarely investigated, and the correlations between the structure, stiffness, and capacitive properties of these materials have not yet been reported. We use electrochemical atomic force microscopy (EC-AFM) to perform in-situ quantitative nanomechanical measurements of two Schiff base metallopolymers, poly[NiSalphen] and its derivative that contains two methoxy substituents in the bridging phenylene diimine unit poly[NiSalphen(CH3O)2], during their polarization in the electrolyte solution to the undoped and fully doped states. We also get insight into the electrochemical p-doping of these polymers using electrochemical quartz crystal microgravimetry (EQCM) coupled with cyclic voltammetry (CV). Combined findings for the structurally similar polymers with different interchain interactions led us to propose a correlation between Young’s modulus of the material, its maximum doping level, and ion and solvent fluxes in the polymer films upon electrochemical oxidation.

The technique of atomic force microscopy (AFM) bending tests of a suspended nano-object (scroll, tube, rod) makes it possible to calculate the Young's modulus of the material it is made of based on experimental data. However, the calculation results involve a large error due to uncertain conditions (console or bridge) of fixing the test object. One of the ways to reduce this error is based on the theoretical consideration of consoles or bridges as beams with one or two ends resting on Winkler elastic foundations. The beam bending problems have been solved in both cases using Krylov's functions. This has allowed for developing an approach to the analytical identification of fixing conditions and including them in the calculations. The application of the approach is illustrated by AFM measurements of the Young's modulus of MgNi_{2}Si_{2}O_{5}(OH)_{4} nanoscrolls.

A group of phyllosilicate nanoscrolls conjoins several hydrosilicate layered compounds with a size mismatch between octahedral and tetrahedral sheets. Among them, synthetic Mg3Si2O5(OH)4 chrysotile nanoscrolls (obtained via the hydrothermal method) possess high thermal stability and mechanical properties, making them prospective composite materials fillers. However, accurate determination of these nano-objects with Young's modulus remains challenging. Here, we report on a study of the mechanical properties evolution of individual synthetic phyllosilicate nanoscrolls after a series of heat treatments, observed with an atomic force microscopy and calculated using the density functional theory. It appears that the Young's modulus, as well as shear deformation's contribution to the nanoscrolls mechanical behavior, can be controlled by heat treatment. The main reason for this is the heat-induced formation of covalent bonding between the adjacent layers, which complicate the shear deformation.

Consoles and bridges of MgNi2Si2O5(OH)4 nanoscrolls were tested for bending in atomic force microscope. Using test data, we analyze how the consoles or bridges were fixed, and took this information into account when calculating the Young's modulus of the nanoscrolls. The results on the consoles are in good agreement with the results on the bridges when modeling the latter as three-span beams, and the former as beams on an elastic foundation with a suspended console.

In atomic force microscopy, the interaction of a probe with a sample is usually controlled by the angle of cantilever bending at a selected point on it using an optical lever. Such control is not designed to record all three components of the interaction-force vector. It is possible to reveal these components and the result of the force action, i.e., the displacement vector of the “nondeformable” probe of an “ideal” cantilever, by additional measurements of the deformation (by the piezoresistive method) or the amount of bending (by the interferometry method) at a selected point, or the bending angle at one more point on the cantilever. In this paper, we present the results of analytical calculation of the optimal location of these points on a cantilever for six combinations of the above three methods, which reduces the measurement error of the components of the force and displacement vectors to a minimum.

The study of the optical response of gold island films revealed an intense line in the light scattering spectrum near 2100 cm-1. Some possible reasons for the appearance of this line are considered. Comparison of the results obtained for films obtained by various technologies, light scattering spectra on other types of samples, as well as comparison with the results of other authors allow us to interpret the line as the result of inelastic light scattering by one-dimensional carbon chains.

The effect of uniaxial tensile stress on the atomic structure and relief of the subsurface layer of molybdenum ribbons has been studied. The destruction of the Mo (100) face with the formation of crystallites was revealed near mouth of the crack. At the same time, the block structures are found to rotate both in the lateral plane and in its perpendicular plane. The surface layer structure in the lateral plane of the ribbon is fragmented into sections, which is associated with the surface relief at different scales. With a help of the concept of multifractal formalism, the spectra of singularities of the initial, loaded and ruptured surface are calculated. It is found that the width of the singularity spectrum, can serve as an indication of the forthcoming rupture.

Background: Nuclear rigidity is traditionally associated with lamina and densely packed heterochromatin. Actively transcribed DNA is thought to be less densely packed. Currently, approaches for direct measurements of the transcriptionally active chromatin rigidity are quite limited. Methods: Isolated nuclei were subjected to mechanical stress at 60 g and analyzed by Atomic Force Microscopy (AFM). Results: Nuclei of the normal fibroblast cells were completely flattened under mechanical stress, whereas nuclei of the cancerous HeLa were extremely resistant. In the deformed HeLa nuclei, AFM revealed a highly-branched landscape assembled of similar to 400 nm closed-packed globules and their structure was changing in response to external influence. Normal and cancerous cells' isolated nuclei were strikingly different by DNA resistance to applied mechanical stress. Paradoxically, more transcriptionally active and less optically dense chromatin of the nuclei of the cancerous cells demonstrated higher physical rigidity. A high concentration of the transcription inhibitor actinomycin D led to complete flattening of HeLa nuclei, that might be related to the relaxation of supercoiled DNA tending to deformation. At a low concentration of actinomycin D, we observed the intermediary formation of stochastically distributed nanoloops and nanofilaments with different shapes but constant width similar to 180 nm. We related this phenomenon with partial DNA relaxation, while non-relaxed DNA still remained rigid. Conclusions: The resistance to deformation of nuclear chromatin correlates with fundamental biological processes in the cell nucleus, such as transcription, as assessed by AFM. General significance: A new outlook to studying internal nuclei structure is proposed.

The optimization of measurements of three spatial components of the probe–sample interaction force and the corresponding “ideal cantilever” displacement vector is considered. To determine these components using an atomic force microscope with the optical beam deflection scheme, it is necessary to measure the bending angles at least at two points on the rectangular cantilever, as well as the torsion angle at any of these points. It is proved analytically that one of the optimal points is the intersection of the probe axis with the cantilever plane. A technique for calculating the optimal position of the other point is developed. An experiment concerning mapping of the force and displacement vector is performed, and satisfactory agreement with the theory is achieved.

Opiate use to treat chronic pain is known to be associated with negative side effects. Therefore, the development of new safe and effective non-opioid analgesics is both important and urgent goal of modern science. Previously, we showed that tetrapeptide Ac-RERR-NH2 has potential as an analgesic drug substance, since it can reduce the excitability of nociceptive neurons responsible for encoding nociceptive signals. The effect of sub-nanomolar concentration of Ac-RERR-NH2 tetrapeptide on embryonic sensory neurons was investigated with the use of atomic force microscopy (AFM) and organotypic tissue culture method. The quasi-static PeakForce QNM AFM mode was used, which allows mapping of local mechanical cell properties. Following administration of the substance, sensory neurons tended to decrease their stiffness. This result is based on the analysis of the values of the apparent Young’s modulus of sensory neurons and their deformation, controlled for the slipping of the tip of the probe over the surface under study. The area index (AI) criterion showed that the studied tetrapeptide has pronounced neurite-stimulating properties. The data obtained suggest that Ac-RERR-NH2, acting at very low concentrations, is able to trigger an as yet unidentified intracellular cascade regulating the growth of neurites of sensory neurons.

The effect of uniaxial tensile stress on the atomic structure and relief of the subsurface layer of molybdenum ribbons has been studied. The destruction of the Mo (100) face with the formation of crystallites was revealed near the crack tip. At the same time, the block structures are found to rotate both in the lateral plane and in its perpendicular plane. The surface layer structure in the lateral plane of the ribbon is fragmented into sections, which is associated with the surface relief at different scales. With a help of the concept of multifractal formalism, the spectra of singularities of the initial, loaded and ruptured surface are calculated. It is found that the width of the singularity spectrum, can serve as an indication of the forthcoming rupture.. Keywords: molybdenum ribbon, mechanical load, annealing, destruction of material, block structures, surface, multifractal formalism.

The study of the optical response of gold island films revealed an intense line in the light scattering spectrum near 2100 cm-1. Some possible reasons for the appearance of this line are considered. Comparison of the results obtained for films obtained by various technologies, light scattering spectra on other types of samples, as well as comparison with the results of other authors allow us to interpret the line as the result of inelastic light scattering by one-dimensional carbon chains. Keywords: inelastic light scattering, gold films, SERS, one-dimensional carbon chains.

The effects of ouabain on the mechanical characteristics of primary sensory neurons and fibroblasts of 10- to 12-day-old chicken embryos were investigated by atomic force microscopy under physiologically relevant conditions. Fibroblasts express only the α1 isoform of Na,K-ATPase, while sensory neurons express the α1 and α3 isoforms. It was found that exposure to ouabain in the concentration corresponding to its endogenous level led to an increase in membrane rigidity of sensory neurons, which was apparently due to activation of the transducer rather than the pumping function of Na,K-ATPase. The mechanical parameters of fibroblasts were not affected by exposure to endogenous concentrations of ouabain. These results suggest that endogenous ouabain specifically modulates the transducer function of the α3 Na,K-ATPase isoform in the sensory neuron membrane. Thus, atomic force microscopy was efficiently applied to perform a comparative study of intracellular signaling cascades in living cells.