Examination of surface adsorption of sodium chloride and sodium dodecyl sulfate by surface potential measurement at the air/solution interface

The surface potential (DeltaV) of the air/sodium chloride solution interface was measured by using an ionizing (241)Am electrode method at 298.2 K. The surface potential steeply increased from 0 up to 15 mV with increasing concentration, then gradually increased up to 20 mV between 1 and 10 mmol dm(-3), and finally stayed almost constant at 20 mV up to the concentration of 20 mmol dm(-3). This result means that sodium ions concentrate more just near the air/solution interface, whereas chloride ions concentrate more far below the interface above the bulk region of electroneutrality. The dipole moment was derived from the surface potential value, from which the width of the interfacial layer was estimated as a function of the magnitude of electric charge. As for the sodium dodecyl sulfate solution, on the other hand, the surface potential steeply decreased from 0 down to -80 mV with increasing concentration from 0 to 0.01 mmol dm(-3), then rapidly increased up to -50 mV between 0.1 and 3 mmol dm(-3), then linearly increased up to 0 mV with increasing concentration from 3 mmol dm(-3) up to the CMC, 8 mmol dm(-3), then quite rapidly decreased again down to -82 mV from the CMC to 10 mmol dm(-3), and finally stayed almost constant at -82 mV up to the concentration of 20 mmol dm(-3). The above variations of the surface potential cannot be elucidated by the conventional surface excess, and therefore, the new concept of surface adsorption was presented for a simple salt and a typical anionic surfactant.     

Characterization of proanthocyanidins in grape seeds using electrospray mass spectrometry

Two proanthocyanidin (PA) fractions, one (Sdp3) with the mean degree of polymerization (mDP) of 3 and the other (Sdp9) with mDP of 9, were obtained from a Vitis vinifera cv. Shiraz grape seed extract. The PA fractions were directly analyzed by electrospray ionization mass spectrometry (ES-MS) and negative ion mass spectra were recorded. The mass spectrum of Sdp3 exhibited only singly charged ions corresponding to the molecular mass of PA with a degree of polymerization (DP) up to 9 (nonamers). In contrast, Sdp9 yielded rather complex mass spectra featuring ions with single [M - H](-), double [M - 2H](2-) and triple [M - 3H](3-) charge representing the molecular masses of PAs up to a DP of 28. In addition, the degree of galloylation per procyanidin (DG) was observed to be up to 5 (pentagallates) in Sdp3 and 8 (octagallates) in the Sdp9. This is the first evidence obtained by mass spectrometry for the distribution of grape seed PAs with such a high degree of polymerization and a broad diversity of galloylation. ES-MS data together with the complementary information provided by acid hydrolysis provides a detailed picture of the composition of grape seed PAs.     

A highly diastereo- and enantioselective copper(I)-catalyzed Henry reaction using a bis(sulfonamide)-diamine ligand

A series of bis(sulfonamide)-diamine (BSDA) ligands were synthesized from commercially available chiral α-amino alcohols and diamines. The chiral BSDA ligand 3a, coordinated with Cu(I), catalyzes the enantioselective Henry reaction with excellent enantioselectivity (up to 99%). Moreover, with the assistance of pyridine, a CuBr-3a system promotes the diastereoselective Henry reaction with various aldehyde substrates and gives the corresponding syn-selective adduct with up to a 99% yield and 32.3:1 syn/anti selectivity. The enantiomeric excess of the syn adduct was 97%.     

Fe-catalyzed regioselective Friedel–Crafts hydroxyalkylation of N-substituted glyoxylamide with indoles

An efficient regioselective Friedel–Crafts hydroxyalkylation of N-substituted glyoxylamide with various indoles catalyzed by Lewis acids was developed. The reactions proceeded smoothly at room temperature and the 2-hydroxy-2-(1H-indol-3-yl)-N-substituted acetamide resulted from the reactions catalyzed by FeSO_4 were synthesized in excellent yields(up to 93%). While the bisindole compounds were obtained when FeCl_3 was used as a catalyst in excellent yields(up to 92%). A possible mechanism was proposed.     

Enantioselective epoxidation of terminal alkenes to (R)- and (S)-epoxides by engineered cytochromes P450 BM-3

Cytochrome P450 BM-3 from Bacillus megaterium was engineered for enantioselective epoxidation of simple terminal alkenes. Screening saturation mutagenesis libraries, in which mutations were introduced in the active site of an engineered P450, followed by recombination of beneficial mutations generated two P450 BM-3 variants that convert a range of terminal alkenes to either (R)- or (S)-epoxide (up to 83 % ee) with high catalytic turnovers (up to 1370) and high epoxidation selectivities (up to 95 %). A biocatalytic system using E. coli lysates containing P450 variants as the epoxidation catalysts and in vitro NADPH regeneration by the alcohol dehydrogenase from Thermoanaerobium brockii generates each of the epoxide enantiomers, without additional cofactor.     

Phonon behavior of CaSnO3 perovskite under pressure

Raman scattering and x-ray diffraction studies of CaSnO(3) perovskite were performed under high-pressure conditions. This high-pressure study was motivated by a recent theoretical study predicting a phase transition in CaSnO(3) from GdFeO(3)-type perovskite to CaIrO(3)-type structure occurred at 12 GPa. Despite no obvious structure change up to a pressure of 26 GPa based on the x-ray diffraction data, high pressure Raman measurements revealed that some Raman modes disappeared upon compression; either merging into neighboring bands or vanishing. The signals for these Raman peaks were recovered during decompression. The measured pressure derivative of Raman shift (?ν∕?P) of CaSnO(3) ranged from ~1.29 to ~4.35, up to 20 GPa. Due to the lack of lattice dynamic study for CaSnO(3) perovskite, the mode symmetry for CaSnO(3) was tentatively assigned based on the empirical relation among Ca-bearing perovskites. The pressure derivative of the Raman shifts was found to be related to their mode vibrations: modes related to Ca and O shifts had a strong pressure dependence compared with those associated with oxygen octahedral rotation.     

Standard thermodynamic properties of H3PO4(aq) over a wide range of temperatures and pressures

The densities and heat capacities of solutions of phosphoric acid, 0.05 to 1 mol kg-1, were measured using flow vibrating tube densitometry and differential Picker-type calorimetry at temperatures up to 623 K and at pressures up to 28 MPa. The standard molar volumes and heat capacities of molecular H3PO4(aq) were obtained, via the apparent molar properties corrected for partial dissociation, by extrapolation to infinite dilution. The data on standard derivative properties were correlated simultaneously with the dissociation constants of phosphoric acid from the literature using the theoretically founded SOCW model. This made it possible to describe the standard thermodynamic properties, particularly the standard chemical potential, of both molecular and ionized phosphoric acid at temperatures up to at least 623 K and at pressures up to 200 MPa. This representation allows one to easily calculate the first-degree dissociation constant of H3PO4(aq). The performance of the SOCW model was compared with the other approaches for calculating the high-temperature dissociation constant of the phosphoric acid. Using the standard derivative properties, sensitively reflecting the interactions between the solute and the solvent, the high-temperature behavior of H3PO4(aq) is compared with that of other weak acids.     

Synthesis of optically active C2-symmetric ketones for the asymmetric epoxidation of prochiral olefins by dioxiranes generated in situ with Caroate as a peroxide source

The new optically active C₂-symmetric ketones 3a (from mannitol) and 3b (from TADDOL) were prepared and the in-situ-generated dioxiranes (with Caroate^TM as peroxide source) were shown to serve as effective oxidants for the asymmetric epoxidation (ee values up to 81%) of prochiral trans and trisubstituted olefins.     

Asymmetric synthesis of aziridines by reduction of N-tert-butanesulfinyl alpha-chloro imines

Reduction of (RS)-N-tert-butanesulfinyl alpha-halo imines afforded chiral aziridines in good to excellent yields. Upon reduction of (RS)-N-tert-butanesulfinyl alpha-halo imines with NaBH4 in THF, in the presence of 10 equiv of MeOH, (RS,S)-beta-halo sulfinamides were formed in excellent yield (up to 98%) with very good stereoselectivity (>98:2). Simple treatment of the latter (RS,S)-beta-halo-tert-butanesulfinamides with KOH afforded the corresponding (RS,S)-N-(tert-butylsulfinyl)aziridines in quantitative yields. On the contrary, its epimer, (RS,R)-N-(tert-butylsulfinyl)aziridine was synthesized by switchover of the reducing agent from NaBH4 to LiBHEt3. (RS,R)-N-(tert-Butylsulfinyl)aziridines were synthesized in good yields (up to 85%) and diastereoselectivity (up to 92:8) by reduction of (RS)-N-tert-butanesulfinyl alpha-halo imines with LiBHEt3 in dry THF and subsequent treatment with KOH. All chiral aziridines were obtained as a single diastereomer after recrystallization (overall yield up to 91%) or after flash chromatography.     

Observation of daunomycin and nogalamycin complexes with duplex DNA using electrospray ionisation mass spectrometry

The noncovalent binding of the antitumour drugs daunomycin and nogalamycin to duplex DNA has been studied using electrospray ionisation mass spectrometry (ESI-MS). The conditions for the preparation of drug/duplex DNA complexes and for their detection by ESI-MS have been optimised. Ions corresponding to these complexes were most abundant relative to free DNA when prepared in the pH range 8-9, and using gentle ESI interface conditions. Self-complementary oligonucleotides, 5'-d(GGCTAGCC)-3' or 5'-d(CGGCGCCG)-3', annealed in the presence of a 5-fold molar excess of either nogalamycin or daunomycin gave ESI mass spectra in which the most intense ions corresponded to three molecules of drug bound to duplex DNA, with some evidence for four drug molecules bound. For binding to 5'-d(TGAGCTAGCTCA)(2)-3', complexes containing up to four nogalamycin and six daunomycin molecules were observed. These data are consistent with the neighbour exclusion principle whereby intercalation occurs between every other base pair such that up to four bound drugs would be expected for the 8 mers and up to six for the 12 mer. Competition experiments involving a single drug in an equimolar mixture of two oligonucleotides (5'-d(TGAGCTAGCTCA)(2)-3' with either 5'-d(CGGCGCCG)(2)-3' or 5'-d(GGCTAGCC)(2)-3') showed ions arising from complexes of drug/5'-d(CGGCGCCG)(2)-3' were more intense than complexes of drug/5'-d(GGCTAGCC)(2)-3', relative to those from the 12 mer in each mixture. While this suggests ESI-MS has the potential to detect differences in sequence selectivity, more detailed experiments involving a comparison of the relative ionisation efficiency of different oligonucleotides and a wider range of intercalators are required to establish this definitively. ESI mass spectra from experiments in which both drugs were reacted with the same oligonucleotide were more complex, such that a clear preference for one drug could not be established.     

Organo-catalyzed highly diastereo- and enantio-selective direct aldol reactions in water

The asymmetric direct aldol reactions of a wide scope of aromatic aldehydes, with unmodified ketones in the presence of 1 mol % of organocatalyst prepared from (2R,3R)-diethyl 2-amino-3-hydroxysuccinate and trans-4-hydroxy-l-proline, were performed in water, affording aldol products in high yields with excellent diastereoselectivities of up to >99:1 and enantioselectivities of up to 98%.     

Extraction of tin by the use of polyurethane foam

Three types of polyurethane foam were tested for the extraction of tin by static and flow systems. The amount of tin extracted varied with the type of foam, acid strength, and chloride and metal-ion concentrations. Quantitative extraction and recovery could be achieved. Open-cell polyurethane foam sponge is thought to act as a "solid solvent-extractant" for tin from aqueous solution. Distribution coefficients up to 5.6 x 10(3) were obtained and the capacity of the foam was up to 8% tin by weight.     

Enhanced luminescence of SiO2:Eu3+ by energy transfer from ZnO nanoparticles

ZnO nanoparticles embedded into SiO(2) by an ex situ method were shown to result in stable green emission with a peak at 510 nm compared to the normal peak at 495 nm from micron-sized ZnO powders. Green emission from ZnO nanoparticles was completely suppressed when they were embedded in SiO2 doped with Eu3+. Instead, the f-f emissions from Eu3+ were enhanced 5-10 times by energy transfer from the embedded ZnO nanoparticles to Eu3+. The Eu3+ luminescence increased as the Eu3+ concentration increased from 1 vs 5 mole % (for 10 mole % ZnO). In addition, the intensity increased as the embedded ZnO nanoparticles concentration increased up to 10 mole % (for 5 mole % Eu3+). The effects of phonon mediated energy transfer, quenching by activator interactions between Eu3+ ions, and energy back-transfer from Eu3+ ions to ZnO nanoparticles were discussed.     

Chiral amine thiourea-promoted enantioselective Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to maleimides

A highly diastereo- and enantioselective Michael addition reaction with respect to prochiral 3-substituted benzofuran-2(3H)-ones and maleimides by a chiral bifunctional thiourea-tertiary amine catalyst was investigated. The corresponding adducts, containing a quaternary center at the C3-position of the benzofuran-2(3H)-one as well as a vicinal tertiary center, were generally obtained in high yields (up to 99%) with very good diastereo- (up to >20:1 dr) and enantioselectivities (up to 97% ee).     

Chiral biscinchona alkaloid promoted asymmetric allylic alkylation of 3-substituted benzofuran-2(3H)-ones with Morita-Baylis-Hillman carbonates

A highly diastereo- and enantioselective asymmetric allylic alkylation reaction with respect to prochiral 3-substituted benzofuran-2(3H)-ones and MBH carbonate by a chiral biscinchona alkaloid catalyst was investigated. The corresponding adducts, containing a quaternary center at the C3-position of the benzofuran-2(3H)-one as well as a vicinal tertiary center, were generally obtained in high yields (up to 97%) with very good diastereo- (up to 98:2 dr) and enantioselectivities (up to 95% ee).     

Improved method for the determination of 4'-epidoxorubicin and seven metabolites in plasma by high-performance liquid chromatography

4'-Epidoxorubicin, its seven metabolites and doxorubicin, as internal standard, were efficiently extracted from plasma using C18 Sep-Pak cartridges. The recoveries ranged from 58% for doxorubicin aglycone up to 98% for 4'-epidoxorubicin glucuronide. The anthracyclines were separated by reversed-phase high-performance liquid chromatography within 9 min and analysed by fluorescence. The assay was sensitive to 3 X 10(-10) M for the glucuronides up to 12 X 10(-10) M for 7-deoxydoxorubicin aglycone. The peak-height ratio of the fluorescence intensities of the anthracyclines versus doxorubicin showed a linear correlation with the concentration from the detection limit up to 2.5 X 10(-7) M (correlation coefficient r2 greater than 0.99). Within-day and between-day precision of the assay were in the ranges 2-14% (n = 6) and 2-11% (n = 6), respectively.     

Electrochemical behavior of riboflavin immobilized on different matrices

The electrochemical behavior of riboflavin (RF) adsorbed on different surfaces of inorganic matrices was investigated using modified carbon paste electrodes. Silica gel and sol-gel silica modified with niobium oxide were denominated as (SN) and (SN(sol-gel)), respectively. These materials were treated with a H3PO4 solution to graft phosphate groups and were denominated as (SNP) and (SNP(sol-gel)). The immobilization of RF on these materials indicated a high electrode stability, avoiding leaching out of the electroactive species (RF) from the electrode surface. The values of formal potential (E0') of the adsorbed RF on the different matrices changed from -283 (SNRF) up to -165 mV (SNPRF(sol-gel)) vs SCE in 0.1 moll(-1) NaNO3 solution at pH 7.0. Compared to the E0' for soluble RF, the values are shifted 183 up to 305 mV toward more positive potentials. The stability of the electrodes and the formal potential of the adsorbed RF on different matrices remained constant upon changing the solution pH from 3 to 8. Some kinetic parameters were estimated; indicating that all systems studied presented a good electron transfer rate.     

Synthesis of 4′-aryl-2′,3′-dideoxynucleoside analogues

A series of 4′-aryl-2′,3′-dideoxynucleoside analogues were synthesized from optically pure 5-oxo-2-aryl-tetrahydrofuran-2-carboxylic acids up to 62% overall yield. 5-Oxo-2-aryl-tetrahydrofuran-2-carboxylic acids were obtained from 2-hydroxy-3-arylcyclopent-2-en-1-ones by asymmetric oxidation in up to 38-57% yield.     

Diastereo- and Enantioselective Cross-Couplings of Secondary Alkylcopper Reagents with 3-Halogeno-Unsaturated Carbonyl Derivatives

Chiral secondary alkylcopper reagents were prepared from the corresponding alkyl iodides with retention of configuration by an I/Li-exchange using tBuLi (−100 °C, 1 min) followed by a transmetalation with CuBr ⋅ P(OEt)₃ (−100 °C, 20 s). These stereodefined secondary alkylcoppers underwent stereoretentive cross-couplings with several 3-iodo or 3-bromo unsaturated carbonyl derivatives leading to the corresponding γ-methylated Michael acceptors in good yields and with high diastereoselectivities (dr up to 96:4). The method was extended to enantiomerically enriched alkylcoppers, providing optically enriched advanced natural product intermediates with up to 90 % ee.     

Formation of NH fragments by electron impact dissociation of ammonia

Excitation functions of the NH(A ³Π-X ³Σ⁻, c ¹Π-a¹Δ) radiation following single-electron impact on ammonia were measured from 9 eV up to 160 eV. Several wavelength intervals of the NH emission spectrum were studied. For the A ³Π-X ³Σ⁻ transition the excitation functions were found to vary with fragment rotation which reveals different dissociation mechanisms for slowly and rapidly rotating fragments. There is a strong indication that at higher impact energies a dissociation channel with simultaneous production of H(2s, 2p) atoms opens up.