AFM methods for studying the morphology and micromechanical properties of the membrane of human buccal epithelium cell.

Using AFM methods in air under normal conditions in a wide range of local force effects ([Formula: see text]< 40 µN) the relief, functional micromechanical properties (elasticity coefficient [Formula: see text], Young's modulus [Formula: see text], elastic [Formula: see text] and plastic [Formula: see text] deformations) and adhesive properties (work [Formula: see text] of adhesive forces [Formula: see text]) of the membranes of living adult cells of human buccal epithelium were studied in the presence of a protective layer < 100 nm of buffer solution that prevented the cells from drying. Almost all geometric and functional characteristics of the membrane in the local approximation at the micro- and nanolevels are affected by size effects and obey the laws of fractal geometry. The Brownian multifractal relief of the membrane is characterized by dimension [Formula: see text] < 2.56 and irregularities < 500 nm vertically and < 2 µm horizontally. Its response to elastic (≤ 6 nN), active (6-21 nN), or passive (> 21 nN) stimulation ([Formula: see text]) is a non-trivial selective process and exhibits a correspondingly elastic ([Formula: see text] 67.4 N/m), active ([Formula: see text] 80.2 N/m) and passive ([Formula: see text] 84.5 N/m) responses. [Formula: see text] and [Formula: see text] depend on [Formula: see text]. Having undergone slight plastic deformations [Formula: see text] < 300 nm, the membrane is capable of restoring its shape. We mapped ([Formula: see text], [Formula: see text] = 2.56; [Formula: see text], [Formula: see text] = 2.68; [Formula: see text], [Formula: see text] = 2.42, [Formula: see text] and [Formula: see text]) indicating its complex cavernous structure.

Study of tribological properties of human buccal epithelium cell membranes using probe microscopy.

In this work demostrates a unique method for determining the absolute value of the friction force of a nanoobject on the surface of a cell membrane using atomic force microscopy. The tribological properties of membranes of adult human buccal epithelium cells in the presence of a protective adsorption buffer layer of ~ 100 nm on their surface were studied using atomic force microscopy in the contact scanning mode. Local mapping of the tribological characteristics of the surface was carried out, viz. friction FL = FL(x, y) and adhesion Fadh = Fadh(x, y) forces were measured. Studies of the friction force Ffr on the membrane surface at the nanolevel showed that its value varies discretely with an interval equal to lLF ≈ 100 nm. It was shown that such discreteness is determined by the interval lLF of the action of adhesive forces Fadh and indicates the fractal nature of the functional dependence of the friction force on the coordinate Ffr = Ffr(x). Thus, for nano-objects with dimensions ≤ lLF, the absolute value of Ffr decreases according to a power law with an increase in the size of the object, which contradicts the similar dependence of the friction force for macro-objects in the global approximation.

[Studies by means of 1H NMR spectroscopy of complex formation of aromatic biologically active compounds with antibiotic topotecan].

The analysis of heteroassociation of antibiotic topotecan (TPT) with aromatic biologically active compounds (BAC): caffeine, mutagens ethidium bromide and proflavine, antibiotic daunomycin, vitamins flavin-mononucleotide and nicotinamide, has been carried out in the work using 1H NMR spectroscopy data. The equilibrium constants of heteroassociation and induced chemical shifts of the protons have been obtained in the complexes with BAC. It is found that the complex formation TPT-BAC has the nature of stacking of the chromophores, additionally stabilized in the case of proflavine by intermolecular hydrogen bond. Calculation of the basic components of the Gibbs free energy of the complexation reactions is carried out, and the factors which stabilize and destabilize the heterocomplexes of molecules are revealed.

Quantification of the interceptor action of caffeine on the in vitro biological effect of the anti-tumour agent topotecan.

Using published in vitro data on the dependence of the percentage of apoptosis induced by the anti-cancer drug topotecan in a leukaemia cell line on the concentration of added caffeine, and a general model of competitive binding in a system containing two aromatic drugs and DNA, it has been shown to be possible to quantify the relative change in the biological effect just using a set of component concentrations and equilibrium constants of the complexation of the drugs. It is also proposed that a general model of competitive binding and parameterization of that model may potentially be applied to any system of DNA-targeting aromatic drugs under in vitro conditions. The main reasons underpinning the proposal are the general feature of the complexation of aromatic drugs with DNA and their interaction in physiological media via hetero-association.

Complete solution of the problem of one-dimensional non-covalent non-cooperative self-assembly in two-component systems.

Equations for the mass conservation law and the molecular parameters observed in spectroscopic experiments have been derived for non-covalent, non-cooperative, one-dimensional self-assembly in systems containing two types of interacting molecules (hetero-association), taking into account "reflected" complexes and "edge effects."