Estimation of the lipophilicity of antiarrhythmic and antihypertensive active 1-substituted pyrrolidin-2-one and pyrrolidine derivatives

The lipophilicity of some antiarrhythmic and antihypertensive active 1-[2-hydroxy- or 1-[2-acetoxy-3-(4-aryl-1-piperazinyl)propyl]pyrrolidin-2-one derivatives (1-12) has been investigated. Their lipophilicity (R(MO) and log k') was determined by reversed-phase thin-layer chromatography and reversed-phase high-performance liquid chromatography with mixtures of acetonitrile and Tris buffer as mobile phases. The partition coefficients of compounds 1-12 (log P(ScilogP)) were also calculated with the ScilogP program. Comparison of R(MO), log k' and calculated log D(7.0 ScilogP) values enabled calculation of clog D(7.0 TLC) and clog D(7.0 HPLC) values. Preliminary quantitative structure-activity relationship studies indicated that for active compounds there is a dependence between affinity for alpha(2)-adrenoceptors and their clog D(7.0 HPLC) values.     

Kinetically controlled Ag+-coordinated chiral supramolecular polymerization accompanying a helical inversion

We report kinetically controlled chiral supramolecular polymerization based on ligand–metal complex with a 3 : 2 (L : Ag⁺) stoichiometry accompanying a helical inversion in water. A new family of bipyridine-based ligands (d-L1, l-L1, d-L2, and d-L3) possessing hydrazine and d- or l-alanine moieties at the alkyl chain groups has been designed and synthesized. Interestingly, upon addition of AgNO₃ (0.5–1.3 equiv.) to the d-L1 solution, it generated the aggregate I composed of the d-L1AgNO₃ complex (d-L1 : Ag⁺ = 1 : 1) as the kinetic product with a spherical structure. Then, aggregate I (nanoparticle) was transformed into the aggregate II (supramolecular polymer) based on the (d-L1)₃Ag₂(NO₃)₂ complex as the thermodynamic product with a fiber structure, which led to the helical inversion from the left-handed (M-type) to the right-handed (P-type) helicity accompanying CD amplification. In contrast, the spherical aggregate I (nanoparticle) composed of the d-L1AgNO₃ complex with the left-handed (M-type) helicity formed in the presence of 2.0 equiv. of AgNO₃ and was not additionally changed, which indicated that it was the thermodynamic product. The chiral supramolecular polymer based on (d-L1)₃Ag₂(NO₃)₂ was produced via a nucleation–elongation mechanism with a cooperative pathway. In thermodynamic study, the standard ΔG° and ΔH_e values for the aggregates I and II were calculated using the van''t Hoff plot. The enhanced ΔG° value of the aggregate II compared to that of the formation of aggregate I confirms that aggregate II was thermodynamically more stable. In the kinetic study, the influence of concentration of AgNO₃ confirmed the initial formation of the aggregate I (nanoparticle), which then evolved to the aggregate II (supramolecular polymer). Thus, the concentration of the (d-L1)₃Ag₂(NO₃)₂ complex in the initial state plays a critical role in generating aggregate II (supramolecular polymer). In particular, NO₃⁻ acts as a critical linker and accelerator in the transformation from the aggregate I to the aggregate II. This is the first example of a system for a kinetically controlled chiral supramolecular polymer that is formed via multiple steps with coordination structural change.

The nanoparticles were transformed into the supramolecular polymer as the thermodynamic product, involving a helical inversion from left-handed to right-handed helicity.     

Dynamic Light Scattering and NMR Studies of Napin

We analyze the structure of napin (BngNAP1), a storage protein (m.w. 14.5 kDa) from Brassica napus. On the basis of the results of ¹H NMR spectroscopy and dynamic light scattering (DLS) studies, the overall shape and secondary structure of the molecule are estimated.     

Square wave adsorptive stripping voltammetric determination of famotidine in urine

Electrochemical studies of famotidine were carried out using voltammetric techniques: cyclic voltammetry, linear sweep and square wave adsorptive stripping voltammetry. The dependence of the current on pH, buffer concentration, nature of the buffer, and scan rate was investigated. The best results for the determination of famotidine were obtained in MOPS buffer solution at pH 6.7. This electroanalytical procedure enabled to determine famotidine in the concentration range 1 × 10⁻⁹–4 × 10⁻⁸ mol L⁻¹ by linear sweep adsorptive stripping voltammetry (LS AdSV) and 5 × 10⁻¹⁰–6 × 10⁻⁸ mol L⁻¹ by square wave adsorptive stripping voltammetry (SW AdSV). Repeatability, precision and accuracy of the developed methods were checked. The detection and quantification limits were found to be 1.8 × 10⁻¹⁰ and 6.2 × 10⁻¹⁰ mol L⁻¹ for LS AdSV and 4.9 × 10⁻¹¹ and 1.6 × 10⁻¹⁰ mol L⁻¹ for SW AdSV, respectively. The method was applied for the determination of famotidine in urine.     

Determination of aluminium and chromium in serum by atomic absorption spectrometry

Summary The optimal conditions for the determination of aluminium and chromium in blood serum are proposed. Several sample pretreatment procedures for the purpose are compared. The best results are obtained by sample dilution with nitric acid (0.1 mol/l) and addition of Mg(NO₃)₂ as modifier with a magnesium concentration of 0.2 mg/ml. This procedure has been used for studying the intestinal intake of aluminium by patients after oral administration of aluminium compounds.     

Surface properties of the binary mixed systems of alkylpyridinium halides and sodium alkylsulfonates

Surface properties of the binary mixed systems of decyl- and dodecylpyridinium chloride or bromide and sodium pentyl- and heptylsulfonate have been investigated. The surface tension of solutions of equimolar mixtures of surfactants and individual surfactants was measured, and the composition of mixed monolayers and surface interaction parameter β were calculated with the regular solution theory. Our results indicate that the properties of mixed films depend on both ionic strength and the kind of added inorganic electrolyte. With the increase of inorganic electrolyte concentration, the content of more surface active ions in the adsorption films enhances and is the highest in the presence of NaI and the smallest when solutions contain NaCl. Mutual interactions in mixed adsorbed films were found to be attractive. However, the strength of interaction weakens with the increase of ionic strength and depends on the kind of inorganic ions in the order: Cl⁻>Br⁻>I⁻.     

Solubility of Solid 2,3-Dimethylbutane and Cyclopentane in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents

The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10^–6 and (2.77 ± 0.94) × 10^–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10^–6 and (4.60 ± 0.76) × 10^–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l ₁₂ were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen.     

Separation of silver from waste waters by ion-exchange resins and concentration by microbial cells

Summary Waste waters of film processing plants are rich with silver. Part of the silver is regenerated electrochemically, but the rest (0.5 g) remains in waste waters and is sent to sewers. This is a bad politic from both the environmental (toxic waste waters) and the economical point of view (a waste of silver). In this work, the silver was isolated by ion-exchange resins and then concentrated by microorganisms. For exchange of silver, Ionenaustauscher I, II and IV were used. The batch method was used to obtain a static equilibrium. Silver elution from exchangers is based on silver transformation to a stable cation or anion complex. By varying the ligands, pH and eluent concentrations, optimum elution is found at 1 mol/l Na₂S₂O₃, 1 mol/l NH₃, 2 mol/l HNO₃ and 1 mol/l (NH₂)₂CO. The concentration of silver in the eluent is about 50 mg/l. The silver ion uptake from solutions after ion exchange by mixed bacterial culture isolated from photographic waste water drain and pure bacterial cultures Escherichia coli 3009 and Bacillus subtilis 3053. was studied. Experiments were carried out in submerse culture at pH 7 with different Ag⁺ concentrations (4, 8 and 40 mg/l) on a rotary shaker (100 rpm) at 37°C. At the lower Ag⁺ concentrations a good growth and simultaneous removal of Ag⁺ from the solutions was achieved. At Ag⁺ concentration of 40 mg/l growth and removal of Ag⁺ by mixed and pure culture differed significantly. Thus mixed bacterial culture grew well and at the same time removed efficiently Ag⁺ (approximately 90%) from medium. Pure bacterial cultures on the contrary were unable to grow at 40 mg/l Ag⁺, though their biomass showed to be an effective biosorbent for Ag⁺ (approximately 80% of Ag⁺ removal).     

Synthesis of 3-substituted-4-hydroxyquinoline N-oxides from the Baylis-Hillman adducts of o-nitrobenzaldehydes

The reaction of the Baylis-Hillman adducts 1b-f derived from o-nitrobenzaldehydes in trifluoroacetic acid in the presence of triflic acid (0.2 equiv.) afforded 3-substituted-4-hydroxyquinoline N-oxides 2b-e and 2a in good to moderate yields. The reaction mechanism was evidenced by the experiment with 1f, the Baylis-Hillman adduct of 2-nitrobenzaldehyde N-tosylimine, as the one involving N-hydroxyisoxazoline as the key intermediate.     

Solvatochromism of 3-[2-(aryl)benzoxazol-5-yl]alanine derivatives

The photophysical properties of N-Boc-3-[2-(9-anthryl)benzoxazol-5-yl]-l-alanine methyl ester (BoxAnt) and N-Boc-3-[2-[4-(9′-(10′-butyl)anthryl)phenyl]benzoxazol-5-yl]-l-alanine methyl ester (BoxPhAnt) were studied in a series of solvents. Their absorption spectra are less sensitive to the solvent polarity than the corresponding fluorescence spectra which show a pronounced solvatochromic effect leading to large Stokes shifts. Using an efficient solvatochromic method, based on the empirical solvent polarity parameter , a large change of the dipole moment on excitation for BoxPhAnt has been found. From an analysis of the solvatochromic behaviour of the absorption and fluorescence spectra in terms of bulk solvent polarity functions, f(_r, n) and g(n), a larger excited-state dipole moment (about 8 D, ψ = 56) was obtained for BoxPhAnt than for BoxAnt (about 3 D, ψ = 0). Both applied methods gave similar values of the excited-state dipole moments for both compounds studied.