Regioselective germylcupration of acetylenes

The reaction of terminal acetylenes with (Ph₃Ge)₂Cu(CN)Li₂ (1) or (Et₃Ge)₂Cu(SMe₂)Li (2) provides vinylgermanes in good yields. Whereas germylcupration of 1-dodecyne gives 2-germyl-1-dodecene as a main product, germylmetalation of phenylacetylene or 3-methyl-3-buten-1-yne affords 1-germyl compounds preferentially.     

Studies on chemical modification of Tulipa gesneriana lectin

Modification of lysine, tyrosine, histidine, aspartic acid and glutamic acid residues did not affect the agglutinating activity of the Tulipa gesneriana lectin (TGL). Modification of two arginine residues per subunit in the lectin with either 2,3-butanedione or phenylglyoxal led to an almost complete loss of activity. An inactive lectin modified with 2,3-butanedione recovered a full activity on dialysis against Tris-HCl buffer. The presence of 0.1 M (alpha-1----6) linked mannotriose, a potent inhibitor of the lectin, protected all the arginine residues from modification and the lectin was fully active. Circular dichroism spectroscopy showed that no significant conformational change of TGL occurred following arginine modification. A treatment of the lectin solution with N-bromosuccinimide or 2-hydroxy-5-nitrobenzyl bromide, chemical reagents for tryptophan modification, caused turbidity of the solution, accompanied with complete loss of activity. The fluorescence emission spectrum of the lectin showed a characteristic tryptophan emission with a maximum centered at 336 nm. Upon addition of manno-oligosaccharides a decrease of the fluorescence intensity was observed, indicating that the environment of tryptophan residues altered. These results suggest that arginine and tryptophan residues are importantly involved in the sugar binding of TGL.     

Copper(II)-cetyltrimethylammonium chloride-chromal blue G ternary complex and its application to the spectrophotometric determination of copper(II)

A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε_630nm = 9.56 × 10³liters · mol⁻¹ · cm⁻¹ is enchanced on ternary complex formation to ε_{542 nm} = 4.78 × 10⁴liters · mol⁻¹ · cm⁻¹. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 10¹⁰ under these conditions.     

The Effect of Fluctuations on Bilayer and Monolayer Systems: High-Resolution X-ray Scattering Study of a Three-Component Lamellar Phase

We have investigated the effect of symmetry on the fluctuation of a three-component lamellar phase composed of oil (octane), water, and a nonionic surfactant (C12E5). The studied lamellae consist of various oil/water volume ratios for a fixed surfactant concentration. From aligned lamellae, we succeeded in obtaining highly reproducible, high-resolution X-ray spectra with very small full width at half maximum (6 × 10⁻⁴Å⁻¹). The deviation of the periodicity expected by the dilution law can be explained from the fluctuations. Measuring this deviation, we observed that for the constant surfactant concentration, lamellae with equal oil/water ratios have higher fluctuation than when oil/water → 0 or ∞ because of the difference of the flexibility of monolayers and bilayers     

Synthesis of trifluoromethylthiazoles and their application to azo dyes

3-Bromo-1,1,1-trifluoropropan-2-one ( 2 ) reacted with thiourea and N-monosubstituted thioureas to give the corresponding 4-trifluoromethylthiazoles, respectively. In the reactions with N,N'-diphenylthiourea and thioamides, the considerably stable intermediates, 4-hydroxy-4-trifluoromethylthiazoline derivatives 7 and 8 , were isolated. The reaction of ethyl 2-bromo-4,4,4-trifluoro-3-oxobutanoate ( 4 ) with thiourea was carried out under the gentle conditions to give both thiazole-5-carboxylate 10 and 4-hydroxythiazoline 11 . The thiazole 10 was applied to the azo dye synthesis and the absorption maxima of thus obtained azo dyes were discussed.     

Preparation characteristics of water-in-oil-in-water multiple emulsions using microchannel emulsification

Microchannel (MC) emulsification is a novel technique for preparing monodispersed emulsions. This study demonstrates preparing water-in-oil-in-water (W/O/W) emulsions using MC emulsification. The W/O/W emulsions were prepared by a two-step emulsification process employing MC emulsification as the second step. We investigated the behavior of internal water droplets penetrating the MCs. Using decane, ethyl oleate, and medium-chain triglyceride (MCT) as oil phases, we observed successful MC emulsification and prepared monodispersed oil droplets that contained small water droplets. MC emulsification was possible using triolein as the oil phase, but polydispersed oil droplets were formed from some of the channels. No leakage of the internal water phase was observed during the MC emulsification process. The internal water droplets penetrated the MC without disruption, even though the internal water droplets were larger than the resulting W/O/W emulsion droplets. The W/O/W emulsion entrapment yield was measured fluorometrically and found to be 91%. The mild action of droplet formation based on spontaneous transformation led to a high entrapment yield during MC emulsification.     

New and efficient dehalogenative coupling and reduction of α-haloketones with active nickel complex. Facile syntheses of 1,4-diketones and bicyclo[4.2.O]oct-3-ene-2,5-diones

The active nickel complex generated in situ by reduction of NiBr₂(PPh₃)₂ with zinc in the presence of Et₄NI is a useful reagent for the dehalogenative coupling of phenacyl halides to 1,4-diaryl-1,4-diketones and for the dechlorination of 3,4-dichlorobicyclo[4.2.0]-octane-2,5-diones to bicyclo[4.2.0]oct-3-ene-2,5-diones.     

A highly sensitive spectrophotometric determination of gallium with chromal blue G in the presence of cetyltrimethylammonium chloride

A new spectrophotometric method for the determination of gallium with chromal blue G in the presence of cetyltrimethylammonium chloride is described. The sensitivity of color reaction between gallium and chromal blue G is greatly increased by the sensitizing action of cetyltrimethylammonium chloride. The gallium complex has maximal absorbance at 662 nm and pH 6.2–6.8. Beer's law is obeyed over the range 0.04–0.6 ppm of gallium. The molar absorptivity of the complex is 1.44 × 10⁵ liters mol^?1 cm^?1 at 662 nm, and the spectrophotometric sensitivity is 4.8 × 10^?4 μg Ga cm^?2. The mole ratio of gallium and chromal blue G in the complex is estimated to be 1:4. The formation constant and effect of interfering ions are described.     

Y-ligation: An efficient method for ligating single-stranded DNAs and RNAs with T4 RNA ligase

Very efficient ligation ofoligodeoxyribonucleotides was attained through asimple molecular construct, which is composed of onestem and two branches (Y-shape), with use of T4 RNAligase. Single-stranded DNAs (naturally, RNAs also) ofmore than 100 nucleotides (even 800 nts) wereconsiderably ligated, approximately as theoreticallyexpected. Owing to the molecular construct adopted,such a tiny amount of ligation products could beamplified to a sufficient amount by PCR and thenrecovered as single-stranded DNAs. This advantage ofbeing amplifiable is shown to be useful for bothcombinatorial chemistry and evolutionary molecularengineering, which deal with a pool of diversity molecules.