Interaction of Nanoparticles in Electrolyte Solutions.

The interaction between nanoparticles includes several components; however, the most frequently used are electrostatic, caused by overlapping double electrical layers, and London-van der Waals interactions, caused by quantum and thermodynamic fluctuations of electromagnetic fields. Only these two kinds of interaction are considered below. The electrostatic interaction is calculated based on the linearized Poisson-Boltzmann equation for particles with constant electrical potential of the surfaces (constant ζ potentials).

Isotropic and Anisotropic Monolayer Structures in RF Discharge Plasma.

We present the results of an experimental and analytical study of the structural and dynamic properties of a monolayer consisting of dust grains in an electrostatic trap in an RF discharge plasma. The possibility of forming a monolayer with an isotropic distribution for interparticle distance and kinetic energy of particles in the structure has been experimentally shown. Isotropy has crucial importance for the study of various processes in such systems, including the kinetics of phase transitions, the formation of directed flows, wave propagation, and others.

Electrostatic interactions between spheroidal dielectric particles.

Theory is developed to address the significant problem of electrostatic interactions between charged polarizable dielectric spheroids. The electrostatic force is defined by particle dimensions and charge, dielectric constants of the interacting particles and medium, and the interparticle separation distance; and it is expressed in the form of an integral over the particle surface. The switching behavior between like charge repulsion and attraction is demonstrated as depending on the ratio of the major and minor axes of spheroids.

Interaction between particles with inhomogeneous surface charge distributions: Revisiting the Coulomb fission of dication molecular clusters.

An analytical solution describing the electrostatic interaction between particles with inhomogeneous surface charge distributions has been developed. For particles, each carrying a single charge, the solution equates to the presence of a point charge residing on the surface, which makes it particularly suitable for investigating the Coulomb fission of doubly charged clusters close to the Rayleigh instability limit. For a series of six separate molecular dication clusters, center-of-mass kinetic energy releases have been extracted from experimental measurements of their kinetic energy spectra following Coulomb fission.

Electrostatic interactions between charged dielectric particles in an electrolyte solution: constant potential boundary conditions.

The problem of electrostatic interactions between colloidal particles in an electrolyte solution has been solved within the Debye-Hückel approximation using the boundary condition of constant potential. The model has been validated in two independent ways - by considering the limiting cases obtained from DLVO theory and comparison with the available experimental data. The presented methodology provides the final part of a complete theory of pairwise electrostatic interactions between spherical colloidal particles; one that embraces all possible chemical scenarios within the boundary conditions of constant potential and constant charge.

Electrostatic interactions between charged dielectric particles in an electrolyte solution.

Theory is developed to address a significant problem of how two charged dielectric particles interact in the presence of a polarizable medium that is a dilute solution of a strong electrolyte. The electrostatic force is defined by characteristic parameters for the interacting particles (charge, radius, and dielectric constant) and for the medium (permittivity and Debye length), and is expressed in the form of a converging infinite series. The limiting case of weak screening and large inter-particle separation is considered, which corresponds to small (macro)ions that carry constant charge.

Amyloid Hydrogen Bonding Polymorphism Evaluated by (15)N{(17)O}REAPDOR Solid-State NMR and Ultra-High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

A combined approach, using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and solid-state NMR (Nuclear Magnetic Resonance), shows a high degree of polymorphism exhibited by Aβ species in forming hydrogen-bonded networks. Two Alzheimer's Aβ peptides, Ac-Aβ(16-22)-NH2 and Aβ(11-25), selectively labeled with (17)O and (15)N at specific amino acid residues were investigated. The total amount of peptides labeled with (17)O as measured by FTICR-MS enabled the interpretation of dephasing observed in (15)N{(17)O}REAPDOR solid-state NMR experiments.

[Structure of amyloid-beta peptides in a complex with model membranes].

Structures of amyloid-beta peptides Aβ1-40, Aβ10-35, Aβ13-23 and Aβ16-22 in a complex with model membranes in solution were obtained on the analysis of NMR experimental data. It has been established that the process of peptide-micelle complex formation occurs through the amino acid residues L17, F19, F20 and G29-M35.

High-resolution NMR structure of the antimicrobial peptide protegrin-2 in the presence of DPC micelles.

PG-1 adopts a dimeric structure in dodecylphosphocholine (DPC) micelles, and a channel is formed by the association of several dimers but the molecular mechanisms of the membrane damage by non-α-helical peptides are still unknown. The formation of the PG-1 dimer is important for pore formation in the lipid bilayer, since the dimer can be regarded as the primary unit for assembly into the ordered aggregates. It was supposed that only 12 residues (RGGRL-CYCRR-RFCVC-V) are needed to endow protegrin molecules with strong antibacterial activity and that at least four additional residues are needed to add potent antifungal properties.

Effect of curcumin on lateral diffusion of phosphatidylcholines in saturated and unsaturated bilayers.

Curcumin, a dietary polyphenol, is a natural spice with preventive and therapeutic potential for neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Curcumin possesses a spectrum of antioxidant, anti-inflammatory, anticarcinogenic, and antimutagenic properties. Because of this broad spectrum of pharmacological activity, it has been suggested that, like cholesterol, curcumin exerts its effect on a rather basic biological level, such as on lipid bilayers of biomembranes.

Micelles and aggregates of oxyethylated isononylphenols and their extraction properties near cloud point.

We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols--C9H19C6H4O(C2H4O)(n)H, where n = 6, 8, 9, 10, or 12--in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols.

[Objectivization of the choice of the amputation level in patients with lower limb critical ischaemia].

The authors compared the informative value of the intraoperative criteria for assessing viability of muscles in high amputations of limbs for chronic critical ischaemia. It was revealed that such signs as subjectively evaluated bleeding, contractility and oedema of muscles possess low specificity in relation to the development of early postoperative complications. Intraoperative macroscopic histochemical study (IHCS) of the activity of muscular tissue lactate dehydrogenase at the level of amputation showed sensitivity of 96,3% and specificity of 92,9 %.

Use of a combination of the RDC method and NOESY NMR spectroscopy to determine the structure of Alzheimer's amyloid Aβ10-35 peptide in solution and in SDS micelles.

The spatial structure of Alzheimer's amyloid Aβ10-35-NH2 peptide in aqueous solution at pH 7.3 and in SDS micelles was investigated by use of a combination of the residual dipolar coupling method and two-dimensional NMR spectroscopy (TOCSY, NOESY). At pH 7.

Micelle structure and molecular self-diffusion in isononylphenol ethoxylate-water systems.

The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)(n)H (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated.

Spatial structure of heptapeptide Aβ(16-22) (beta-amyloid Aβ(1-40) active fragment) in solution and in complex with a biological membrane model.

The spatial structure of an active fragment of beta-amyloid Aβ(1-40) heptapeptide Aβ(16-22) (Lys-Leu-Val-Phe-Phe-Ala-Glu) in aqueous buffer solution and in complex with sodium dodecyl sulfate micelles as a model membrane system was investigated by (1)H NMR spectroscopy and two-dimensional NMR (TOCSY, HSQC-HECADE (Heteronuclear Couplings from ASSCI-domain experiments with E.COSY-type crosspeaks), NOESY) spectroscopy. Complex formation was confirmed by the chemical shift changes of the heptapeptide's (1)H NMR spectra, as well as by the signs and values of the NOE effects in different environments.

[Intra-operative histochemical detection of vitalized muscular tissue during lower limb amputation for chronic critical ischemia].

Direct results of 747 lower limb amputations for chronic critical lower limb ischemia were analyzed. Early postoperative complications were observed in 45,1% of cases. Among them 45,4% were caused by tissue ischemia.

Lateral diffusion in sphingomyelin bilayers.

Sphingomyelin (SM) is an important lipid of eukaryotic cellular membranes and neuronal tissues. We studied lateral diffusion in macroscopically oriented bilayers of synthetic palmitoylsphingomyelin (PSM) and natural sphingomyelins of egg yolk (eSM), bovine brain (bSM) and bovine milk (mSM) by pulsed field gradient NMR (PFG NMR) in the temperature range 45-60 °C. We found that the mean values of lateral diffusion coefficients (LDCs) of SMs are 1.

Aggregation of amyloid Abeta((1-40)) peptide in perdeuterated 2,2,2-trifluoroethanol caused by ultrasound sonication.

Ultrasound sonication of protein and peptide solutions is routinely used in biochemical, biophysical, pharmaceutical and medical sciences to facilitate and accelerate dissolution of macromolecules in both aqueous and organic solvents. However, the impact of ultrasound waves on folding/unfolding of treated proteins, in particular, on aggregation kinetics of amyloidogenic peptides and proteins is not understood. In this work, effects of ultrasound sonication on the misfolding and aggregation behavior of the Alzheimer's Abeta((1-40))-peptide is studied by pulsed-field gradient (PFG) spin-echo diffusion NMR and UV circular dichroism (CD) spectroscopy.

[Effectiveness of new diagnostic drug Diaskintest in children for tuberculosis diagnostic].

DST was ascertained to have a high sensitivity in virtually all patients with tuberculosis and a positive reaction was first noted in the infected. With stabilization and regression, the response to DST was much less pronounced than that in clinical and primary infection (that to the Mantoux test being more evident). DST showed its use as a marker of active tuberculosis not only in its local forms, but also in latent tuberculous infection.

[An NMR study of the temperature dependence of the coefficient of water self-diffusion through lipid bilayer membranes].

The temperature dependence of the coefficient of water self-diffusion through plane-parallel lipid multilayers of the phospholipid dioleoylphosphatidylcholine oriented on a glass support has been studied in the temperature range of 20-60 degrees C by the method of NMR with magnetic field pulse gradient. The values of the coefficients of transbilayer water diffusion are by four orders of magnitude less than for bulky water and ten times less than the coefficients of lateral diffusion of the lipid under the same conditions. The temperature dependence of the coefficient of water diffusion is described by the Arrhenius law with an apparent activation energy of about 41 kJ/mol, which far exceeds the activation energy for the diffusion of bulky water (18 kJ/mol).

[Comparative analysis of tuberculosis morbidity in children and adolescents from Moscow and the Penza Region].

Tuberculosis morbidity was comparatively analyzed in the children and adolescents of Moscow and the Penza Region. The epidemiology of tuberculosis in the children and adolescents was established to be universal in the compared regions in the study period. This manifested itself as a stable tendency for higher morbidity rates (MR), increased incidence of destructive tuberculosis, inadequate use of the existing methods for active detection of tuberculosis in these age groups, and, among those who had fallen ill with this disease, an increase in the number of persons from the foci of tuberculous infection and persons with established contact with patients with tuberculosis.

[State of water and its diffusion across lipid bilayers: effect of hydration degree].

The state of adsorbed water (estimated from the dependence of the shape of the 1H NMR spectrum on the angle between the normal to the bilayers and the direction of the magnetic field) and the diffusion of water molecules in the direction of the normal to the bilayers (estimated by 1H NMR spectroscopy with the impulse gradient of magnetic field) in microscopically oriented dioleoylphosphatidylcholine bilayers have been studied depending on hydration. The dependences of the shape of the NMR spectrum on angle differ qualitatively only at concentrations of water greater and less than the concentration that is achieved upon hydration from saturated vapors chi(eq) (about 23 weight %). At concentrations below chi(eq), all water present in samples enters the hydrate shells of polar "heads" of lipids or is in the state of "rapid exchange" with the water of hydrate shells, with the result that the signal of spin echo for water is observed only in a narrow range of angles close to the "magic angle", 54 degrees C.

[Lateral diffusion of saturated phosphatidylcholines in cholesterol-containing bilayers].

Lateral diffusion in oriented bilayers of saturated cholesterol-containing phosphatidylcholines, dipalmitoylphosphatidylcholine and dimyrilstoylphosphatidylcholine upon their limiting hydration has been studied by NMR with impulse gradient of magnetic field. For both systems, similar dependences of the coefficient of lateral diffusion on temperature and cholesterol concentration were observed, which agree with the phase diagram showing the presence of regions of ordered and unordered liquid-crystalline phases and a two-phase region. Under similar conditions, the coefficient of lateral diffusion for dipalmytoylphosphatidylcholine has lower values, which is in qualitative agreement with its greater molecular mass.

[Preoperative diagnosis of metastatic involvement of perirectal lymph nodes].

Condition of perirectal lymph nodes was examined by endorectal sonography in 93 patients with rectal cancer prior to surgery. Precision of diagnosis of involvement by endorectal sonography was 62.5% and depended on the size of lymph node.