Quantitative correlation of the in vitro biological effect with parameters of molecular complexation in mutagen-interceptor systems

According to the theory of interceptor-protector action a quantitative link between the physico-chemical parameters of molecular complexation and in vitro biological effect in aromatic drug-interceptor systems must exist. In the present communication such link between relative change in mutagenicity of IQ-type aromatic mutagens on addition of aromatic interceptor molecules with equilibrium hetero-association constants of mutagen-interceptor complexation has been found using the published in vitro data in bacteria cell system

Magnetocaloric effect and magnetization in a Ni-Mn-Ga Heusler alloy in the vicinity of magnetostructural transition

The magnetic and thermodynamic properties of a Ni2.19Mn0.81Ga alloy with coupled magnetic and structural (martensitic) phase transitions were studied experimentally and theoretically. The magnetocaloric effect was measured by a direct method in magnetic fields 0-26 kOe at temperatures close to the magnetostructural transition temperature. For theoretical description of the alloy properties near the magnetostructural transition a statistical model is suggested, that takes into account the coexistence of martensite and austenite domains in the vicinity of martensite transformation point.Comment: presented at ICM-2003, to appear in JMM

General statistical-thermodynamical treatment of one-dimensional multicomponent molecular hetero-assembly in solution

A general treatment has been developed for the multicomponent one-dimensional non-covalent molec-ular hetero-assembly in solution using transfer matrix and sequence generating function approaches. The main result is set of equations, which allows one to obtain any thermodynamical quantities of the mul-ticomponent system and, in particular, experimental observable enabling one to get all equilibrium parameters of molecular interaction. The matrix form of presentation of the key equations allows their direct incorporation into matrix-oriented mathematical software, which leads to a two orders of magni-tude increase in speed of calculation of as compared to other known approache

Complexation of aromatic drugs with single-walled carbon nanotubes

We report a detailed study of the complexation of aromatic molecules and drugs with the surface of single-walled carbon nanotubes (SWCNTs, the diameter and the length ranges are 0.5-2 nm and 1-5 μm, respectively) in terms of equilibrium binding constants, K. It is found that the binding constants have magnitudes of the order of 104-105 M-1 and that there is some ligand specificity to the SWCNT surface depending on the structure of the aromatic molecul

Interceptor effect of C₆₀ fullerene on the in vitro action of aromatic drug molecules

In this work we are focusing on studying the influence of the pristine C₆₀ fullerene on biological activity of some aromatic drug molecules in human buccal epithelial cells. Assessment of the heterochromatin structure in the cell nucleus as well as the barrier function of the cell membrane was performed. The methods of cell microelectrophoresis and atomic force microscopy were also applied. A concentration-dependent restoration of the functional activity of the cellular nucleus after exposure to DNA -binding drugs (doxorubicin, proflavine and ethidium bromide) has been observed in human buccal epithelial cells upon addition of C₆₀ fullerene at a concentration of ~10−5

Evidence of entropically driven C₆₀ fullerene aggregation in aqueous solution

In the present work, we report the first experimental evidence of entropically driven C₆₀ fullerene aggregation in aqueous solution, occurring with nearly zero enthalpy chang

The theory of interceptor-protector action of DNA binding drugs

The review discusses the theory of interceptor-protector action (the IPA theory) as the new selfconsistent biophysical theory establishing a quantitative interrelation between parameters measured in independent physico-chemical experiment and in vitro biological experiment for the class of DNA binding drugs. The elements of the theory provide complete algorithm of analysis, which may potentially be applied to any system of DNA targeting aromatic drugs. Such analytical schemes, apart from extension of current scientific knowledge, are important in the context of rational drug design for managing drug's response by changing the physico-chemical parameters of molecular complexatio

Study of the properties of doxorubicin-resistant cells affected by acute leucosis

The stiffness of cell membrane was found to be one of the factors determining resistance of a cell in vitro to antibiotic doxorubicin action.The data obtained have important prognostic value in studying drug resistance of tumour blood cells and can be used as objective markers of efficiency of the antitumor therap

First-principles study of lattice instabilities in the ferromagnetic martensite Ni2_2MnGa

The phonon dispersion relations and elastic constants for ferromagnetic Ni$_2$MnGa in the cubic and tetragonally distorted Heusler structures are computed using density-functional and density-functional perturbation theory within the spin-polarized generalized-gradient approximation. For $0.9<c/a<1.06$, the TA$_2$ tranverse acoustic branch along $[110]$ and symmetry-related directions displays a dynamical instability at a wavevector that depends on $c/a$. Through examination of the Fermi-surface nesting and electron-phonon coupling, this is identified as a Kohn anomaly. In the parent cubic phase the computed tetragonal shear elastic constant, C$^\prime$=(C$_{11}-$C$_{12}$)/2, is close to zero, indicating a marginal elastic instability towards a uniform tetragonal distortion. We conclude that the cubic Heusler structure is unstable against a family of energy-lowering distortions produced by the coupling between a uniform tetragonal distortion and the corresponding $[110]$ modulation. The computed relation between the $c/a$ ratio and the modulation wavevector is in excellent agreement with structural data on the premartensitic ($c/a$ = 1) and martensitic ($c/a$ = 0.94) phases of Ni$_2$MnGa.Comment: submitted to Phys. Rev.

First-principles calculation of the instability leading to giant inverse magnetocaloric effects

The structural and magnetic properties of functional Ni-Mn-Z (Z=Ga, In, Sn) Heusler alloys are studied by first-principles and Monte Carlo methods. The ab initio calculations give a basic understanding of the underlying physics which is associated with the strong competition of ferro- and antiferromagnetic interactions with increasing chemical disorder. The resulting d-electron orbital dependent magnetic ordering is the driving mechanism of magnetostructural instability which is accompanied by a drop of magnetization governing the size of the magnetocaloric effect. The thermodynamic properties are calculated by using the ab initio magnetic exchange coupling constants in finite-temperature Monte Carlo simulations, which are used to accurately reproduce the experimental entropy and adiabatic temperature changes across the magnetostructural transition