Synthesis and structure of bis- and tris-ferrocene containing N-methylimide foldamers

The synthesis and conformational analysis of dimer Fc–CO–NMe–CO–Fc (5) and trimer Fc–CO–NMe–CO–Fn–CO–NMe–CO–Fc (6) have been described. It has been shown by means of spectroscopic studies, X-ray crystallography, and molecular modeling, that these molecules are dominated by cis–cis conformation. Furthermore, we recognized for the first time, that such type of organometallics possess elements of chiral helicity. Their crystal lattices are characterized by π–π and CH–π intermolecular interactions (5) and by CH?OC intermolecular hydrogen bonds (6). We believe that foldamers 5/6 are stabilized by the special type of aromatic π–π interactions between the closer cyclopentadienyl rings of the juxtaposed ferrocene units.     

Forces between a hard surface and an air–aqueous interface with and without films

The adsorption of particles to air–aqueous interfaces is vital in many applications, such as mineral flotation and the stabilization of food foams. The forces in the system determine whether a particle will attach to an air–aqueous interface. The forces between a particle and an air–aqueous interface are influenced by Derjaguin–Landau–Verwey–Overbeek forces (i.e. van der Waals and electrostatic forces), non–Derjaguin–Landau–Verwey–Overbeek forces (e.g. hydrophobic, hydrodynamic, structural, and capillary forces), liquid drainage, and liquid flow. As an air–aqueous interface can be deformed by a particle, the forces measured between an air–aqueous interface and a particle can differ from those measured between two hard surfaces separated by liquid. The presence of a film at an air–aqueous interface can also change the forces.     

Mineral content and physical properties of local and imported honeys in Saudi Arabia

In addition to color, ash and electrical conductivity (EC), the levels of 14 minerals were investigated in 23 varieties of honey from Saudi Arabia and six other countries. The quantities of the macrominerals obtained were as follows (in ppm): K (298.60–491.40), Mg (80.70–199.30), Ca (60.75–99.95), P (21.10–33.29), and Na (15.69–26.93). The quantities of trace minerals were as follows (in ppm): Fe (67.18–98.13), I (12.61–94.68), Mn (4.15–6.04), Zn (3.44–5.72), Li (1.15–4.26), Co (1.00–1.32), and Ni (0.15–0.67). The quantities of the heavy metals Pb and Cd were found to be 0.06–0.23 and 0.00–0.16, respectively. The values of the tested elements—color, ash and EC—varied among the tested honeys according to their botanical origin. Dark honeys, especially acacia honeys, had higher elemental content and EC values than lighter ones. Saudi and Yemeni seder honeys exhibited no distinctive characteristics in their tested parameters. The levels of heavy metals indicated that the tested honeys were safe for human consumption.     

Viscosities of Binary and Ternary Mixtures of Water,Alcohol, Acetone,and Hexane

This articles studied and determined the viscosities of the binary mixtures of water–methanol, water–ethanol, water–propanol, water–acetone, acetone–ethanol, methanol–ethanol, and acetone–hexane and the ternary mixtures of water–methanol–ethanol and water–ethanol–acetone at 20°C. It is shown that the mixing of water with the alcohols and acetone resulted in a positive deviation of viscosity, which reached the maximum value at the water mole fraction x ₁ ～ 0.7 for water–methanol, x ₁ ～ 0.72 for water–ethanol, x ₁ ～ 0.74 for water–propanol, and x ₁ ～ 0.83 for water–acetone binary mixture. This viscosity deviation can be mainly attributed to the formation of micelles of alcohol or acetone molecules in water because of the hydrophobic attraction between the hydrocarbon chains. The micelle surfaces are surrounded by hydration layers, leading to the positive viscosity deviation in the liquid mixtures because the water in hydration layers has a much higher viscosity than bulk water. Also, the contrary observation was found in the binary mixtures of acetone–ethanol and acetone–hexane, having a negative viscosity deviation.     

Experimental measurement and thermodynamic modelling of clathrate hydrate equilibria and salt solubility in aqueous ethylene glycol and electrolyte solutions

We present the extension of a recently developed method for modelling saline water to the thermodynamic prediction of phase behaviour for mixed salt–organic clathrate hydrate inhibitor aqueous solutions. Novel freezing point, boiling point and salt solubility data have been generated for NaCl–ethylene glycol (EG) and KCl–EG aqueous solutions. These data have been used in the optimisation of binary interaction parameters between salts and ethylene glycol. The extended thermodynamic model is capable of predicting complex vapour–liquid–solid (VLSE) equilibria for aqueous electrolytes and/or organic inhibitor solutions over a wide range of pressures, temperatures and inhibitor concentrations. Reliable hydrate dissociation data for two mixed salt–organic inhibitor quaternary systems (CH₄–H₂O–NaCl–EG and CH₄–H₂O–KCl–EG) have been measured at pressures up to 50 MPa. These data are used to validate the predictive capabilities of the model for hydrate equilibria. Good agreement between experimental data and predictions is observed, demonstrating the reliability of the developed model.     

Thermodynamic investigations of uranium-rich binary and ternary alloys

Uranium–zirconium, uranium niobium, and uranium–zirconium–niobium alloys were synthesized by the arc melting technique and their phase transition temperatures were determined using a high temperature calorimeter. Heat capacities of U–7 wt%Zr, U–7 wt%Nb, U–5 wt%Zr–2 wt%Nb, U–3.5 wt%Nb–3.5 wt%Zr, and U–2 wt%Zr–5 wt%Nb were measured using a differential scanning calorimeter in the temperature range 303–921 K. A set of self-consistent thermodynamic functions such as entropy, enthalpy, and Gibbs energy function data for these binary and ternary alloys were reported for the first time using heat capacity data obtained in this study and required literature data.     

Stoichiography in the study of spatial heterogeneity of the chemical composition and structure of thin films and nanostructured systems

We present the principles of stoichiography and a reference-free stoichiographic differential (separating) dissolution method used to study the composition and structure of thin films and nanostructured systems: HTS films with 123 different compositions, Al–Au–Sn–Co–Mn, Si/SiO₂/Ni(Cr)–Cu–Cu2S, Cr–Cu–S, and Cu–S multilayer films, Bi–Ti–O films on Ru/SiO₂/Si, Mn_1–xZn _x S, and ZnS–EuS supports, and also nanostructured manganese ferrite in borate glass matrices, nanodisperse composite sorbents and the Co–Si–Pt–O/Al₂O₃ catalyst modified by Pt nanoparticles, and oxide catalyst precursor Fe₂Co/Al₂O₃ for the synthesis of carbon nanotubes.     

Synthesis and Antibacterial Activity of Water-soluble Chitin Derivatives

Diethylaminoethyl–chitin (DEAE–chitin) was synthesized by introducing DEAE groups onto the C(6)–OH in chitin. DEAE–chitin was N-deacetylated by heating in aqueous 10% sodium hydroxide containing sodium borohydride to prepare the diethylaminoethyl–chitosan (DEAE–chitosan). In addition, DEAE–chitin was quaternized with ethyl halide to produce triethylaminoethyl–chitin (TEAE–chitin). Their antibacterial activities were evaluated by using colony count against Staphylococcus aureus and Escherichia coli by means of shake flask method. The antibacterial activity was found to increase in order of DEAE–chitin, DEAE–chitosan, TEAE–chitin. DEAE–chitin was hydrolyzed by enzymes to investigate the effect of molecular weight on its antibacterial activities. The antibacterial activity was dependent on the structure, particularly on the molecular weight of chitin derivatives. © 1997 John Wiley & Sons, Ltd.     

Metal distribution and binding in balneological peats and their aqueous extracts

Binding of metals in typical bath peat samples (“Großes Gifhorner Moor”, Sassenburg/North Germany) and their aqueous extracts was characterized by means of a multi-method approach. For that purpose a sequential extraction procedure based on peat-filled chromatography columns was developed. Water-soluble metal and DOM (dissolved organic matter) fractions were subdivided by use of a stepwise increased pH gradient (pH 3.8–5), finally by the chelator EDTA and 0.1 mol L^–1 hydrochloric acid. Metal fractions very strongly bound to peat were assessed by an aqua regia extraction. Metal determinations required were performed by atomic spectrometry methods (AAS, ICP–OES, and TXRF). The metal and DOM concentrations in the peat extracts varied significantly, depending on the natural variety of the peat matter under study (e.g., Al: 25–674, Cd: 0.05–0.2, Cu: 5– 15.4, Fe: 77–1785, Mn: 21–505, Ni: 2–33, Pb: < 1, Zn: 9– 715 (μg L^–1); Na: 8–45, K: 1.3–14.9, Ca: 2–51, Mg: 1.1– 7.9 (mg L^–1); 26–73 mg L^–1 DOC). An increase of the pH increased the DOC (dissolved organic carbon) of the peat extracts, but hardly the concentration of heavy metals. The latter could only be re-mobilized by EDTA and dilute hydrochloric acid. Additional investigations of the peat extracts using tangential-flow ultrafiltration revealed that the heavy metals extracted at pH < 4 were predominantly dissociated. At higher pH (pH > 4.5) they were preferentially bound to macromolecular DOM. Moreover, using multistage ultrafiltration the size distribution of the DOM and their metal species was assessed.     

The 11S proteasome activator: Isolation from mouse brain and the influence on peptide substrate hydrolysis of the 20S and 26S proteasomes

Purification of the 11S proteasome regulator from mouse brain was optimized; the subunit composition of the isolated protein was determined by Western blot. The dependency of 20S proteasome peptidase activity on the molar concentration of the 11S regulator was examined. The Michaelis constants of hydrolysis of the specific fluorescent substrates Suc–Leu–Leu–Val–Tyr–AMC, Ac–Arg–Leu–Arg–AMC, and Z–Leu–Leu–Glu–AMC by the 20S proteasome from BALB/c mouse brain and the 20S–11S complex were determined. It was shown that the 11S particle has almost no influence on binding of specific fluorescent substrates to the 20S proteasome, but strongly accelerates hydrolysis of all three substrates, while not affecting the rate of peptide substrate hydrolysis by the 26S proteasome.     

Syntheses of (+)- and (–)-Methyl 8-Epinonactate and (+)- and (–)-Methyl Nonactate

In four synthetic steps, (+)- and (–)-methyl 8-epinonactate ((+)- and (–)? 4 ) have been derived from (+)- and (–)-7-oxabicyclo[2.2.1]heptan-2-one ((+)- and (–)? 9 ), respectively. The (+)- and (–)-methyl nonactate ((+)- and (–)? 3 ) were obtained from (+)- and (–)? 4 , respectively, by Mitsunobu displacement reactions. Optical resolution of (±)? 9 via chromatographic separation of the corresponding N-methyl-S-alkyl-S-phenylsulfoximides 24 and 25 yielded the starting materials (+)- and (–)? 9 , respectively.     

Physicochemical transformations in multicomponent melts containing uranium,zirconium, and iron oxides and calcium silicates and aluminates

The properties and crystallization nature of melts of the U⁴⁺–U⁶⁺–Zr⁴⁺–Fe²⁺–Fe³⁺–Ca²⁺–Si⁴⁺–Al³⁺–O^2– system were studied. It was found that the main factors changing the physicochemical characteristics of the melt are the concentration and valence state of uranium and the concentrations of iron oxide and silicon oxide. The results obtained in the analysis of the physicochemical properties of the multicomponent melt can be used in nuclear power engineering to preclude disintegration of a WWER type nuclear reactor in the course of a hypothetical severe reactor accident.     

Trithia- and dithiaselenapentalenes from benzylidene-1,2-dithioles and heterocumulenes

Deprotonation of the 5-aryl-3-benzyl-1λ⁴,2-dithiol-1-ylium iodides ( 6a–6d ) obtained by reaction of the 1-aryl-4-phenylbutan-1,3-diones ( 5a–5d ) with hydrogen sulfide and iodine in ethanol gave the stable 5-aryl-3-benzylidene-3H-1,2-dithioles ( 3a–3d ), respectively. The dithioles ( 3a–3d ) underwent thermal cycloaddition reactions with isoselenocyanates and isothiocyanates to give the 2-(substituted amino)-5-aryl-3-phenyl-6,6aλ⁴-dithia-1-selenapentalenes ( 7a–7h ) andthe 2-(substituted amino)-5-aryl-3-phenyl-1,6,6aλ⁴-trithiapentalenes ( 8a–8l ), respectively. The dithioles( 3a–3d ) reacted with isocyanates to give the N-substi-tuted-2-phenyl-2-(5-aryl-3H-1,2-dithiol-3-ylidene) acetamides ( 11a–11h ). © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8 : 233–244, 1997.     

Immunoaffinity Chromatography Clean-Up and LC for Analysis of Salinomycin and Narasin in Chicken Muscle

A method has been developed for simultaneous analysis of salinomycin and narasin in chicken muscle. Muscle samples were extracted with acetonitrile. Clean-up of the extracts on an immunoaffinity chromatography column was followed by liquid chromatography with postcolumn derivatisation and UV–visible detection at 520 nm. The immunoaffinity columns were prepared by coupling the anti-salinomycin monoclonal antibody to CNBr-activated Sepharose 4B. When chicken muscle fortified at 5, 25, and 50 ng g^?1 was analyzed, intra-assay mean recoveries of salinomycin and narasin were in the ranges 87.5–93.1 and 86.2–94.3%, respectively, with relative standard deviation (RSD) of 4.7–6.2 and 2.4–5.7%. Inter-assay mean recoveries were 86.0–93.0 and 86.0–92.1%, respectively, with RSD of 4.8–6.5 and 5.8–7.4%. The limit of detection of the method was 2.5 ng g^?1 for both drugs in chicken muscle.     

Interactions of glucose and polyacrylamide in solutions and gels

The swelling of polyacrylamide (PAAm) gels increased with rising glucose concentrations, and so did the osmotic pressure of the soluble polymer and its intrinsic viscosity. A Flory–Huggins‐based model for the osmotic pressure of a nonionic hydrophilic polymer in a ternary solution consisting of a main solvent, a polymer, and a nondissociating low‐molecular‐weight cosolute was developed and examined. The model‐calculated values were in reasonably good agreement with experimental results for the water–PAAm–glucose system studied when PAAm–water and glucose–water interaction coefficients from the binary systems were used, and only the PAAm–glucose interaction coefficient was adjusted. Its negative value suggested a favorable interaction of glucose and PAAm, supporting the notion of glucose being a good cosolvent for PAAm. Isothermal titration microcalorimetry results showed no evidence for the binding of glucose to PAAm, but an exothermic interaction was indicated between glucose and PAAm. Microcalorimetrically determined enthalpic contributions to the Flory–Huggins interaction coefficients showed enthalpically favorable binary interactions, particularly the enthalpic component of the PAAm–glucose interaction coefficient (χ_H23), which was slightly negative. The enthalpically favorable interaction between glucose and PAAm may explain the increased osmotic pressure of PAAm in glucose solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3053–3063, 2003     

Head-to-head vinyl polymers. VI. Preparation and characterization of head-to-head poly(allyl alcohol) and its esters

Head-to-head (H–H) poly(allyl alcohol) (PAA) was prepared by the LiAlH₄ reduction of H–H poly(methyl acrylate) obtained from the methylation of alternating copolymer of ethylene with maleic anhydride. H–H poly(allyl acetate) (PAAc) and H–H poly(allyl benzoate) (PABz) were further derived by means of its acylations. All of these three H–H polymers were characterized by IR, NMR, TGA, and PGC measurements. The corresponding head-to-tail (H–T) polymers were also prepared by a similar method from the conventional H–T polymer of methyl acrylate, and characterized to allow comparison with the H–H polymers. The softening temperatures of all H–H polymers were somewhat higher than those of the respective H–T polymers, probably suggesting that the H–H placements increased the stiffness of the polymers. Unlike poly(acrylic esters) reported previously, these H–H allyl polymers were found to degrade at temperatures slightly lower than the H–T polymers. On pyrolysis at 430°C, both PAAc and PABz were also observed to release predominantly acetic acid and benzoic acid, respectively, and small quantities of the corresponding allyl ester monomers. The molar ratios of acid to ester were substantially larger for H–H polymers.     

Densitometry and indirect normal‐phase HPTLC–ESI–MS for separation and quantitation of drugs and their glucuronide metabolites from plasma

The present work describes novel methods using densitometry and indirect or off‐line high performance thin‐layer chromatography–mass spectrometry (HPTLC–MS) for the simultaneous detection and quantification of asenapine, propranolol and telmisartan and their phase II glucuronide metabolites. After chromatographic separation of the drugs and their metabolites the analytes were scraped, extracted in methanol and concentrated prior to mass spectrometric analysis. Different combinations of toluene and methanol–ethanol–n‐butanol–iso‐propanol were tested for analyte separation and the best results were obtained using toluene–methanol–ammonia (6.9:3.0:0.1, v/v/v) as the elution solvent. All of the drug–metabolite pairs were separated with a homologous retardation factor difference of ≥22. The conventional densitometric approach was also studied and the method performances were compared. Both of the approaches were validated following the International Conference on Harmonization guidelines, and applied to spiked human plasma samples. The major advantage of the TLC–MS approach is that it can provide much lower limits of detection (1.98–5.83 pg/band) and limit of quantitation (5.97–17.63 pg/band) with good precision (?3.0% coefficient of variation) compared with TLC–densitometry. The proposed indirect HPTLC–MS method is simple yet effective and has tremendous potential in the separation and quantitation of drugs and their metabolites from biological samples, especially for clinical studies.     

Preparation and properties of polyarylates and copolyarylates from phenylindanedicarbonyl chloride and bisphenols

A series of polyarylates having inherent viscosities of 0.4–1.1 dL/g was prepared by the two phase polycondensation of 1,1,3-trimethyl-3-(4-chloroformylphenyl)indanecarbonyl chloride with various bisphenols in an organic solvent–aqueous alkaline solution system in the presence of a phase transfer catalyst. Similarly, copolyarylates of high molecular weights were prepared from a mixture of the phenylindanedicarbonyl chloride, terephthaloyl chloride, and 2,2-bis(4-hydroxy-phenyl)propane. All the polyarylates were characterized by their amorphous nature and high solubility in organic solvents. They gave transparent and tough films by the solution casting. The films had tensile strength of 33–46 MPa, elongation at break of 3–16%, and tensile modulus of 1.2–1.6 GPa. These polyarylates had glass transition temperatures in the range of 205–310°C, and began to decompose at ca. 350°C in air.     

Functionalization of short multi-walled carbon nanotubes with creatinine and aromatic aldehydes via microwave and thermal methods and their influence on the MKN45 and MCF7 cancer cells

The chemical functionalization of carboxylated short multi-walled carbon nanotubes (Sh–MWCNT–COOH) by creatinine (Sh–MWCNT–amide) and later modification with aromatic aldehydes for producing 2-amino-5-arylidene-1-methyl-1H–imidazol-4(5H)-one (Sh–MWCNT–imidazols) via thermal and microwave methods have been investigated. All the products were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, elemental analysis, thermogravimetric analysis, derivative thermogravimetric and cellular investigations. These functionalizations have been chosen due to the active sites of CC and carbonyl groups in Sh–MWCNT–imidazols, which might be used as functional materials in the future. MTT assay was used to examine the behavior of cell proliferation after 72 h of cell culture experiments. Cellular investigations were performed for two kinds of cells, human breast and gastric cancer cells. Cellular results showed high toxicity of modified Sh–MWCNTs on the gastric cancer cells compared to breast cells.     

Spectrophotometric determination of carbamazepine and mosapride citrate in pure and pharmaceutical preparations

Simple, rapid and sensitive spectrophotometric methods were developed for the determination of carbamazepine and mosapride citrate drugs in pure and pharmaceutical dosage forms. These methods are based on ion pair and charge transfer complexation reactions. The first method is based on the reaction of the carbamazepine drug with Mo(V)–thiocyanate in hydrochloric acid medium followed by an extraction of the coloured ion-pair with 1,2-dichloroethane and the absorbance of the ion pair was measured at 470 nm. The second method is based on the formation of ion-pairs between mosapride citrate and two dyestuff reagents namely bromothymol blue (BTB) and bromocresol green (BCG) in a universal buffer of pH 4 and 3, respectively. The formed ion-pairs are extracted with chloroform and methylene chloride and measured at 412 and 416 nm for BTB and BCG reagents, respectively. The third method is based on charge transfer complex formation between mosapride citrate (electron donor) and DDQ (π-acceptor reagent) and the absorbance of the CT complexes was measured at 450 nm. All the optimum conditions are established. The calibration graphs are rectilinear in the concentration ranges 10–350 for carbamazepine using Mo(V)–thiocyanate and 4–100, 4–60 and 10–150 μg mL^?1 for mosapride citrate using BTB, BCG and DDQ reagents, respectively. The Sandell sensitivity (S), molar absorptivity, correlation coefficient, regression equations and limits of detection (LOD) and quantification (LOQ) are calculated. The law values of standard deviation (0.04–0.09 for carbamazepine using Mo(V)–thiocyanate and 0.022–0.024, 0.013–0.018 and 0.013–0.020 for mosapride citrate using BTB, BCG and DDQ, respectively) and relative standard deviation (0.630–2.170 for carbamazepine using Mo(V)–thiocyanate and 0.123–1.43, 0.102–0.530 and 0.226–1.280 for mosapride citrate using BTB, BCG and DDQ, respectively) reflect the accuracy and precision of the proposed methods. The methods are applied for the assay of the two investigated drugs in pharmaceutical dosage forms. The results are in good agreement with those obtained by the official method.