ABSTRACT
The magnetic structure of the mixed rare-earth system Pr x Y1-x Fe3(BO3)4 (x = 0.75, 0.67, 0.55, 0.45, 0.25) was studied via magnetic and resonance measurements. These data evidence the successive spin reorientation from the easy-axis antiferromagnetic structure formed in PrFe3(BO3)4 to the easy-plane one of YFe3(BO3)4 associated with the weakening of the magnetic anisotropy of the Pr subsystem due to its diamagnetic dilution by nonmagnetic Y. This reorientation occurs through the formation of an inclined magnetic structure, as was confirmed by our previous neutron research in the range of x = 0.67 ÷ 0.45. In the compounds with x = 0.75 and 0.67 whose magnetic structure is close to the easy-axis one, a two-step spin reorientation takes place in the magnetic field H||c. Such a peculiarity is explained by the formation of an interjacent inclined magnetic structure with magnetic moments of Fe ions located closer to the basal plane than in the initial state, with these intermediate states remaining stable in some ranges of the magnetic field. An approach based on a crystal field model for the Pr(3+) ion and the molecular-field approximation is used to describe the magnetic characteristics of the system Pr x Y1-x Fe3(BO3)4. With the parameters of the d-d and f-d exchange interactions, of the magnetic anisotropy of the iron subsystem and of the crystal field parameters of praseodymium thus determined, it is possible to achieve a good agreement between the experimental and calculated temperature and field dependences of the magnetization curves (up to 90 kOe) and magnetic susceptibilities (2-300 K).
ABSTRACT
The optical activity of DNA liquid-crystalline dispersions is being investigated based on a theory for absorption of electromagnetic waves by large molecular aggregates. The impact on the dispersions-optical properties, exerted by the interaction between the complexes of nucleic acid molecules and nanoparticles, is being considered.
Subject(s)
Circular Dichroism , DNA/chemistry , Liquid Crystals/chemistry , Nanoparticles/chemistry , Models, Theoretical , Nucleic Acid ConformationABSTRACT
A problem on the electrostatic interaction of two homogeneously charged macromolecular rods of a finite length, submerged into an electrolyte solution was considered. An explicit expression for the energy of interaction and rotational moment as a function of the angle of rotation between the long axes of the molecules was obtained. At small angles of rotation, the expression for energy turns into the corresponding formula for parallel rods, and the rotational moment tends to zero, as it follows from geometrical considerations. The possibility is discussed whether the study is applicable to real biological systems, including liquid-crystalline dispersions of DNA.
Subject(s)
Macromolecular Substances/chemistry , Algorithms , DNA/chemistry , Static Electricity , ThermodynamicsABSTRACT
Three variants of the model for the formation of "bridges" between the nucleic acid molecules fixed in the structure of particles of liquid-crystalline dispersions were considered. What the three variants have in common is that the bridges represent polymeric chelate cross-links consisting of alternating molecules of daunomycin and copper ions. The differences between the three variants are that in the first variant, the bridges begin and end with daunomycin molecules that form a complex by the mechanism of external binding with nucleic acids; in the second variant, the bridges begin and end with copper ions coupled with the pairs of bases of nucleic acids; and in the third variant, the bridges begin with the daunomycin molecule and end with the copper ion. For each variant, a mathematical model was constructed, which describes the formation of bridges, and equations of binding were derived. The results of calculations were compared with the experimental data. Within the framework of each variant, the values of the energy of interaction between the daunomycin molecule and the copper ion in the bridge, the energy of interaction of the daunomycin molecule with the nucleic acid, and the length of the bridge were varied. For all variants, those values of the parameters were chosen that fit best the experimental data. The theoretical curves obtained using the three variants of the model agree rather well with the family of experimental curves. The best agreement between the theoretical and experimental data was obtained when the polymeric chelate bridge includes more than two daunomycin molecules.
Subject(s)
Nucleic Acids/chemistry , Adsorption , Crystallization , Daunorubicin/chemistry , Models, Chemical , ThermodynamicsABSTRACT
Serum titer achieved while producing antibodies to Y. pseudotuberculosis surface antigens with the use of colloid gold as adjuvant was as high as that achieved with the use of Freund's complete adjuvant (1:10,240). Still the amount of the antigen introduced when colloid gold particles were used as adjuvant was lower by 2 orders. The study revealed that colloid gold used as antigen carrier activated the phagocytic activity of lymphoid cells.
Subject(s)
Adjuvants, Immunologic , Antibodies, Bacterial/immunology , Gold Colloid , Yersinia pseudotuberculosis/immunology , Animals , Antibodies, Bacterial/biosynthesis , Antigens, Bacterial/immunology , Gold Colloid/immunology , Immunization/methods , RabbitsABSTRACT
Right-handed helical double-stranded DNA molecules were shown to interact with chitosans to form under certain conditions (chitosan molecular weight, content of amino groups, distance between amino groups, ionic strength and pH of solution) cholesteric liquid-crystalline dispersions characterized by abnormal positive band in CD spectrum in the absorption region of DNA nitrogen bases. Conditions were found for the appearance of intense negative band in CD spectrum upon dispersion formation. In some cases, no intense band appeared in CD spectrum in spite of dispersion formation. These results indicate not only the multiple forms of liquid-crystalline dispersions of DNA-chitosan complexes but also a possibility to control the spatial properties of these complexes. The multiplicity of liquid-crystalline forms of DNA-chitosan complexes was attempted to explain by the effect of character of dipoles distribution over the surface of DNA molecules on the sense of spatial twist of cholesteric liquid crystals resulting from molecules of the complexes.
Subject(s)
Chitin/chemistry , DNA/chemistry , Chitin/analogs & derivatives , Chitin/metabolism , Chitosan , Crystallization , DNA/metabolism , Hydrogen-Ion Concentration , Models, Chemical , Molecular Weight , Optics and Photonics , Osmolar Concentration , SolutionsABSTRACT
Abnormal optical properties of liquid-crystalline dispersions (phases) formed as a result of phase exclusion of double-stranded DNA and RNA from water-salt poly(ethylene glycol) solutions and X-ray parameters of these phases are compared. It is shown that the cholesteric packing of nucleic acid molecules is realized at the certain osmotic pressure of a solvent only. A comparison of the optical properties of liquid-crystalline phases (dispersions) to their X-ray parameters allows one to put forward a suggestion on various hydratation (fluctuation) regimes of the nucleic acid behaviour under the condensed phases formation and factors, influencing the mode of packing of these molecules in phases formed. It is shown as well, that immobilization of DNA cholesteric liquid-crystalline particles in the content of polymeric matrix is accompanied by the stabilization of these particles and, hence, their specific abnormal optical activity as well as by formation of particles having a structure, which corresponds to the "optically isotropic ordered liquid" without abnormal optical activity. Data on stabilization of the cholesteric structure of liquid-crystalline DNA dispersions by creation of polymeric chelate bridges between the neighbouring DNA molecules, fixed in the structure of liquid-crystalline dispersions, are shown.
Subject(s)
DNA/chemistry , Nucleic Acid Conformation , RNA/chemistry , Animals , Crystallography, X-Ray , Molecular Structure , Polyethylene GlycolsABSTRACT
The influence of interface irregularities on synchrotron radiation Mössbauer filtration at an isotope interface is examined theoretically. Calculations are performed for a random-roughness interface model for a (56)Fe/(57)Fe isotope interface. The analysis shows that, despite a drop in the efficiency in the real structures compared with the idealized structures, the efficiency of Mössbauer filtration of synchrotron radiation remains high enough to ensure a successful experiment. In particular it was found that, as well as a regular saw-like profile of the external interface, a randomly rough profile of the external interface may also be used in the Mössbauer filtration experiment if the roughness parameters satisfy certain demands.
ABSTRACT
The study of the use of ozone-containing solutions in 40 experimental animals and in 58 patients with diffuse purulent peritonitis revealed their marked detoxicant effect that manifested with early decrease of ESR, leucocytosis, plasma concentration of bilirubin and medium-size molecules, and microbes. Lethality in the experimental and control group were 5.2 and 16.6% respectively.
Subject(s)
Ozone/therapeutic use , Peritonitis/drug therapy , Postoperative Complications/drug therapy , Adolescent , Adult , Animals , Humans , Male , Middle Aged , Postoperative Period , Rats , Solutions , Time FactorsABSTRACT
The circular dichroism spectra of liquid-crystalline dispersions formed of double-stranded DNA molecules were calculated. It was found that the amplitude and sing of the anomalous band in these spectra in the region of absorption of nitrous bases depend on the size of dispersed particles, the pitch of their cholesterol helix and the sign of its spatial winding. The theoretical calculations are compared with experimental data characterizing the anomalous optical properties of liquid-crystalline DNA dispersions and synthetic polynucleotides formed as a result of phase elimination in aqueous salt solutions of polyethyleneglycol. The theoretically calculated circular dichroism spectra of liquid-crystalline DNA dispersions agree with the circular dichroism spectra of these dispersions observed experimentally.
