Fine Tuning of Heme Reactivity: Hydrogen-Bonding and Dipole Interactions Affecting Ligand Binding to Hemoproteins

Heme reactivity in hemoproteins is governed by the microenvironment near the ligand binding site. In order to quantify polarity effects on heme ligand binding, the kinetics of O₂ and CO binding have been measured for a series of synthetic heme models equipped with a range of groups of varying dipole moments positioned near the heme coordination site. For hemes with polar aprotic groups, both O₂ on (k′) and off rates (k) are found to be dependent on the dipole moment. For model systems containing protic groups, the O₂ off rate is substantially reduced due to hydrogen bonding with the coordinated O₂. The hydrogen-bonding stabilization is estimated to be 0.7 and 1.6 kcal/mol for an alcohol and a secondary amide, respectively. CO binding displays little correlation with a polarity effect; instead it seems to depend upon the size and position of the polar group.     

Tumor pleural effusion proteome profiling for ovarian cancer biomarkers mining

Mass spectrometric proteome profiling of tumor pleural effusion (TPE) liquid fraction from ovarian cancer patients was performed to identify the potential biomarkers of the disease. The methodology of analysis of the TPE protein composition included the removal of high-abundant proteins by affinity chromatography, additional fractionation of the low-abundant proteins based on their lipophilicity, and high-resolution mass spectrometric analysis. As a result, 190 proteins were indentified, 49% of them belonging to the groups of extracellular and membrane proteins. The application of several criteria to data analysis allowed us to generate a group of 26 proteins that are promising candidates for testing as ovarian cancer biomarkers.     

Structures of branched oligophenylenes studied by NMR spectroscopy

A series of model cyclotrimers was studied by NMR spectroscopy using 2D COSY, HSQC, and HMBC correlations to establish the structures of branched oligophenylenes, whose branching center is the 1,3,5-triphenyl-substituted benzene ring.     

Synthesis, crystal structure, and luminescent properties of a silver(I) perrhenate complex with phenazine

The silver complex with phenazine [Ag(Phz)₂(H₂O)]ReO₄ (Phz is C₁₂H₈N₂) has been synthesized, and its crystal structure has been determined. The crystals are triclinic: space group $P\bar 1$ , a = 9.587(1) Å, b = 10.875(1) Å, c = 11.668(1) Å, α = 104.98(1)°, β = 103.87(1)°, γ = 92.94(1)°, V = 1132.6(2) ų, Z = 2, ρ_calc = 2.160 g/cm³. The structure is composed of the [Ag(Phz)₂(H₂O)]⁺ silver cationic complexes and ReO ₄ ^? anions. The Ag⁺ ion is coordinated by two nitrogen atoms of independent phenazine molecules and the water oxygen atoms and has a T-shaped coordination (Ag-N_av 2.223 Å, Ag-O_w 2.498(8) Å). Phenazine, being an electron-donor ligand, forms columns due to π-π stacking interaction between the aromatic groups. The water molecules form hydrogen bonds with the oxygen atoms of water molecules of neighboring complexes and with oxygen atoms of the ReO ₄ ^? anions.     

Wetting behavior of pulmonary surfactant aqueous solutions

The wetting properties of pulmonary surfactant aqueous solutions with respect to solid surfaces with different degree of hydrophobicity have been studied. The contact angles θ of drops from a pulmonary surfactant solution onto SiO₂-glass surfaces have been measured as a function of their degree of hydrophobicity θ _w. The completely hydrophilic SiO₂-glass surface is essentially hydrophobized by the animal-derived pulmonary surfactant Curosurf. The hydrophobization depends on the surfactant concentration—the contact angles increase with increasing the Curosurf concentration C _s in the low concentration range, but they remain almost constant in a wide range of C _s >90 μg/ml. Additions like NaCl and bovine serum albumin influence the θ-values. The contact angles θ naturally increase with increasing θ _w but this dependence is not linear—the curve steepens at larger θ _w values. The thickness h of the wetting thin liquid films from Curosurf aqueous solutions depends on the hydrophobicity θ _w of the solid surface and the h(θ _w) curves always pass a minimum. The h-values, as well as the h(θ _w) curve, are mainly determined by the steric and hydrophobic disjoining pressures, which depend on the orientations and conformations of the molecules adsorbed on the solid surface from the very complicated multi-component aqueous solutions.     

Electrochemical and Transport Characteristics of Membrane Systems in the Electronanofiltration Separation of Solutions Containing Ammonium Nitrate and Potassium Sulfate

Russian Journal of Electrochemistry - Electrochemical and transport characteristics of systems equipped with OPMN-P and OFAM-K membranes during operation in electronanofiltration cell are studied...     

Synthesis and biological properties of novel structural analogs of isothiobarbamine

Russian Chemical Bulletin - Novel structural analogs of isothiobarbamine, which differ from the prototype scaffold by the substituent at position 2 of the pyrimidine heterocycle, were for the first...     

Dielectric properties of liquid-crystal azomethine polymer with a side alkyl-substituted chain,doped with fullerene C<Subscript>60</Subscript>

We studied the actual and imaginary components of the dielectric constant of liquid-crystal azomethine polymer with a side chain, doped with 0.5 wt % of fullerene C₆₀, over a wide range of temperatures and frequencies; measurements were made by means of dielectric spectroscopy. By analyzing the frequency dependence of the dielectric constant, we detected the relaxation processes (α, β₁, and β₂) in the nanocomposite, corresponding to certain modes of molecular motion and described them by the Arrhenius equations (β₁- and β₂-processes) and the Vogel–Fulcher–Tamman equation (α-process). An antiplasticization effect is discovered after doping the polymer with fullerene C₆₀, which manifests itself in increasing the glass transition temperature of the nanocomposite compared to this parameter typical of pure polymer.