Enhancement effect of cysteine on anodic stripping voltammetry of copper

The anodic stripping behaviour of copper in the presence of compounds with a mercapto group, such as cysteine, was investigated. In the presence of cysteine, a copper stripping wave at ?0.12 V vs. SCE decreased, and instead a new sharp wave was observed at more positive potential. Its peak height increased with increasing concentration of cysteine, and at 1 × 10^?5M cysteine it became about seven times as large as that observed in the absence of cysteine. Then the method using this enhanced wave was studied for the determination of trace cupric ion. The results were that the relative standard deviation for five repetitive determinations was about 4% at 10^?8M Cu(II) and the detection limit was 6 × 10^?10M Cu(II). From the investigation by means of cyclic voltammetry, it was found that this enhanced wave was due to the transformation from a cupric—cysteinate complex to a mercuric—cysteinate complex.     

An ab initio MO study on the structures and electronic states of hydrogen-bonded O3- HF and SO2-HF complexes

Ab initio molecular orbital (MO) calculations have been carried out for base-hydrogen fluoride (HF) complexes (base = O3 and SO2) in order to elucidate the structures and energetics of the complexes. The ab initio calculations were performed up to the QCISD(T)/6-311++G(d,p) level of theory. In both complexes, hydrogen-bonded structures where the hydrogen of HF orients toward one of the oxygen atoms of bases were obtained as stable forms. The calculations showed that cis and trans isomers exist in both complexes. All calculations for the SO2-HF complex indicated that the cis form is more stable in energy than the trans form. On the other hand, in O3-HF complexes, the stable structures are changed by the ab initio levels of theory used, and the energies of the cis and trans forms are close to each other. From the most sophisticated calculations (QCISD(T)/6-311++G(d,p)//QCISD/6-311+G(d) level), it was predicted that the complex formation energies for cis SO2-HF, trans SO2-HF, cis O3-HF, and trans O3-HF are 6.1, 5.7, 3.4, and 3.6 kcal/mol, respectively, indicating that the binding energy of HF to SO2 is larger than that of O3. The harmonic vibrational frequencies calculated for cis O3-HF and cis SO2-HF complexes were in good agreement with the experimental values measured by Andrews et al. Also, the calculated rotation constants for cis SO2-HF agreed with the experiment.     

Preparation and Characterization of SiO2-MxOy(M = V, Sn, Sb) Thin Films from Silicic Acid and Metal Chlorides

The preparation of SiO₂-M _x O _y (M = V, Sn, Sb) binary oxide thin films by sol-gel method was investigated. The reaction of silicic acid with metal chloride (M = Sn and Sb) or oxychloride (M = V) formed homogeneous solutions. The dip-coating of slide glass and silicon wafer followed by heat treatment gave oxide films having Si—O—M bond. The changes of FT-IR spectra as a function of heat treatment temperature and molar composition confirmed the Si—O—M bonds. The sheet resistance of films increased with an increase on heat treatment temperature and decrease in the content of metal oxide M _x O _y . X-ray diffraction peaks were observed for the SiO₂-V₂O₅ films with high V₂O₅ contents and heat-treated above 250°C, while the others were amorphous. Oxide films heat treated at 500°C had a thickness between 340–470 nm.     

Fallout241Am concentration in food and human tissue

Americium and plutonium concentrations in food samples and human tissue samples were determined using alpha-ray spectrometry.Food samples, representative of the average dietar intake over a period of 30d in Japan, were pruchased in Akita during 1985 and 1986. The food was divided into six groups: cereals, vegetable, fruits/beans, seaweeds, fish/shellfish, and meats/eggs/milk. Most of the. total ingestion of both Pu and Am was contributed by seaseed and fish/shellfish. The concentration of Am in the other food groups was low.A compoarison of the measured²⁴¹Am/^239+240Pu ratio in human liver with the predicted value of the ICRP-30 or ICRP-48 model showed that the half-life of Am in the liver is approximately 2–10y. The human tissue samples were obtained from subjects who died in Akita and Niigata Prefectures in northern Japan during 1981–1984. The median concentration of²⁴¹Am was 1.4 mBq/kg-wet in the stemum (n=11), 3.4 mBq/kg-wet in the liver (n=19), and 0.5 mBq/kg-wet in the lung (n=15). The ratio of²⁴¹Am/^239+240Pu was 0.34 in the sternum, 0.12 in the liver, and 0.14 in the lung.     

Solute partition study in aqueous sodium dodecyl sulfate micellar solutions for some organic reagents and metal chelates

The partition constants (K _d) have been estimated for nitrophenols, thiazolylazo dyestuffs and metal chelate compounds into the sodium dodecyl sulfate (SDS) micellar phase at an ionic strength of 0.10M [(H⁺, Na⁺)Cl^–] and at 20 °C. The equilibrium partition data obtained by batch-wise solution spectrophotometry (equilibrium shift method) agree well with those by the micellar electrokinetic capillary chromatography (MECC) with the SDS micellar pseudo-stationary phase. The MECC clearly discriminates a very small difference (0.03) in the logK _d values of some metal chelates. The plot of theK _d values with the van der Waals volume of the solute molecules obviously shows the leveling-off of theK _d values over solute size near 110 ml/mol, which seems to be consistent with the results obtained in the Triton X-100 micellar system. This phenomenon arises most probably from the rigidity of the micellar pseudo-phase (a micellar volume-constraint effect) in sharp contrast with true two-phase partitioning such as solvent extraction systems.     

Synthesis of 4,8-anhydro-d-glycero-d-ido-nonanitol 1,6,7-trisphosphate as a novel IP3 receptor ligand using a stereoselective radical cyclization reaction based on a conformational restriction strategy

4,8-Anhydro-d-glycero-d-ido-nonanitol 1,6,7-trisphosphate (9), designed as a novel IP₃ receptor ligand having an α-C-glycosidic structure, was synthesized via a radical cyclization reaction with a temporary connecting allylsilyl group as the key-step. Phenyl 2-O-allyldimethylsilyl-3,4-bis-O-TBS-1-seleno-β-d-glucopyranoside (10a), conformationally restricted in the unusual ¹C₄-conformation, was treated with Bu₃SnH/AIBN to form the desired α-cyclization product 16a almost quantitatively. On the other hand, when a conformationally unrestricted O-benzyl-protected 2-O-allyldimethylsilyl -1-selenoglucoside 15 was used as the substrate, the radical reaction was not stereoselective and gave a mixture of the α-and β-products. From 16a, the target C-glucoside trisphosphate 9 was synthesized via phosphorylation of the hydroxyls by the phosphoramidite method. During the synthetic study, an efficient procedure for the oxidative C-Si bond cleavage, via a nucleophilic substitution at the silicon with p-MeOPhLi followed by Fleming oxidation, was developed. The C-glycoside 9 was found to be a full agonist for Ca²⁺ mobilization, although its activity was weaker than that of the natural ligand IP₃. Thus, the α-C-glucosidic structure was shown to be a useful mimic of the myo-inositol backbone of IP₃.     

Membrane properties of cationic liposomes composed of dipalmitoylphosphatidylcholine and dipalmityldimethylammonium bromide

Cationic liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and dipalmityldimethylammmonium bromide (DPAB) were prepared by the Bangham method and the effect of DPAB on the membrane properties was examined in terms of liposomal shape, particle size, trapping efficiency, surface potential and dispersibility. The dispersibility of the mixed DPPC/DPAB liposomes (the mole fraction of DPAB (X_DPAB)  0.05) was excellent and the dispersibility was maintained for 6 months, since the zeta-potential of the mixed liposomes was approximately +40 mV. The trapping efficiency of the mixed DPPC/DPAB liposomes (X_DPAB = 0.05) was 10 times greater than that of the DPPC liposomes, and the value was largest among the mixed liposomes (X_DPAB = 0–1.0). Freeze-fracture electron micrographs indicated that the shape of the mixed DPPC/DPAB liposomes (X_DPAB = 0.05) was that of large unilamellar vesicles (LUVs) with a diameter of approximately 2 μm, while the shape of the DPPC liposomes was that of multilamellar vesicles (MLVs). The mixed liposomes had, therefore, a high trapping efficiency. Furthermore, the shape of the mixed DPPC/DPAB liposomes (X_DPAB = 0.75) was also that of LUVs with a diameter of approximately 2 μm and these had a high trapping efficiency. Whereas, the particle size (500 nm) of the mixed DPPC/DPAB liposomes (X_DPAB = 0.25) was smaller than that of the former and had the minimum trapping efficiency. The phase transition temperature of the liposomal bilayer membranes indicated a maximum value at 0.25–0.30 mole fractions of DPAB. These facts were considered to be due to the fact that DPPC and DPAB, whose molar ratio was 7.5:2.5, were tightly packed in the liposomal bilayer membranes and that the curvature of the liposomal particle was resultantly large. Nevertheless, LUVs having a high trapping efficiency were easily obtained by mixing a small amount of DPAB with the DPPC.     

Thermodynamics of surfactant-dye complex formation in aqueous solutions. Sodium alkyl sulfates and azo oil dye systems

Thermodynamics of surfactant-dye complex formation have been studied, in terms of equilibrium coefficient, using a spectrophotometer. The systems are 6 sodium alkyl sulfates, which have different alkyl chain lengths, and 4-phenylazo-1-naphthylamine. A pronounced spectral change in the dye solution occurs on addition of the surfactant; the change has a definite isosbestic point and a new absorption band at 535 nm because of surfactant-dye complex formation, which is caused by hydrophilic-hydrophilic interaction. As the alkyl chain length in the surfactant increases, the values of free energy change (negative) increase, while the value of enthalpy change (negative) increases and the value of entropy change (positive) decreases. The longer the alkyl chain length in surfactant increase, the more stable the surfactant-dye complex becomes.Surfactant-dye complex will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.     

Micellar size, shape and counterion binding of N-(1,1-Dihydroperfluoroalkyl)-N,N,N-trimethylammonium chloride in aqueous solutions

Under the limiting conditions, light-scattering method was applied to determine the size and shape of fluorinated micellar structure in aqueous solution. The hydrodynamic radii (r _h) of molecular aggregates were investigated for four amphiphiles with different alkyl chain length: N-(1,1-dihydroperfluorooctyl)-, N-(1,1-dihydroperfluorodecyl)-, N-(1,1-dihydroperfluorododecyl)-, and N-(1,1-dihydroperfluorotetradecyl)-N,N,N-trimethylammonium chloride by dynamic light scattering. Size of these molecular aggregates drastically increased with increasing carbon number of alkyl chain and the concentration. For example, the r _h values were 35, 63, 95, and 136 nm for C8, C10, C12, and C14 of the alkyl chain, respectively, at the concentration of 15× critical micelle concentration (cmc) and at 298.2 K. On the other hand, the mean radius of gyration (r _g) and the apparent molecular weight of these aggregates were measured using static light scattering. The r _g value was found to be 34, 73, and 125 nm for C8, C10, and C12 of the alkyl chain, respectively, at the same condition above. The shape of aggregate was analyzed by comparing the dependence of r _g/r _h with theoretical values. The plots of r _g against r _h almost corresponded with the theoretical line of oblate ellipsoid (disk-like), and which was also expected from calculation of packing parameter value. The measurement for chloride ion activity was made by a chloride ion selective electrode to know the degree of counterion binding to the aggregates, whose values increased with increasing total concentration and with the carbon number of alkyl chain. The chloride ion binding to aggregates neutralized cationic head groups under their electrostatic repulsion and partly promoted the growth of aggregates.     

Interfacial properties of branch-tailed fluorinated surfactants yielding a water/supercritical CO2 microemulsion

We have examined the interfacial properties of several fluorinated surfactants in a water/CO2 mixture with a pendant drop tensiometer and revealed the relationships between the interfacial properties, the surfactant structure, and the microemulsifying power. We employed the following Aerosol-OT analogue surfactants that have two fluorinated tails: bis(1H,1H,5H-octafluoropentyl)-2-sulfosuccinate (di-HCF4), sodium bis(1H,1H,9H-hexadecafluorononyl)-2-sulfosuccinate (di-HCF8), sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), and sodium bis((1H,1H,2H,2H-heptadecafluorodecyl)-oxyethylene)-2-sulfosuccinate (8FS(EO)4). To discuss the effect of the fluorocarbon/hydrocarbon ratio in single surfactant molecules, water/CO2 interfacial tension (IFT) of a hybrid surfactant with one fluorocarbon and one hydrocarbon tail, that of a surfactant with a single fluorinated tail, and that of a hydrocarbon surfactant, Aerosol-OT (AOT), were examined. The hybrid surfactant employed was sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-hexanesulfonate (FC6-HC4), and the single-tailed surfactant was perfluoropolyether ammonium carboxylate (PFPECOONH4, CF3CF2(CF2OCF(CF3))4COONH4). All of the fluorinated AOT analogue surfactants exhibited an excellent level of activity at the water/CO2 interface compared with other fluorinated surfactants and AOT. With a larger hydrocarbon chain number in the CO2-philic tails (i.e., from 0 to 2), the IFT of the AOT analogue surfactants was increased. The area occupied by one surfactant molecule at the water/CO2 interface, A, and the critical microemulsion concentration, cmicroc, were determined and used to examine the water-to-surfactant molar ratio within a reversed micelle, W0c, of the surfactants. The surfactants that form W/scCO2 microemulsions with a large W0c were found to lower the interfacial tension efficiently irrespective of increases in temperature. To achieve the most desirable W0C, the surfactant needs not only a high CO2-philicity of the tails but also a high Krafft point, properties which induce a low hydrophilic/CO2-philic balance.