NMR study on the photoresponsive DNA tethering an azobenzene. Assignment of the absolute configuration of two diastereomers and structure determination of their duplexes in the trans-form

Two diastereomers of a photoresponsive oligodeoxyribonucleotide tethering a trans-azobenzene, based on the chirality of the central carbon of a diol linker, were separated by reversed-phase HPLC. On the basis of 2D NMR analysis, absolute configurations of the diastereomers alpha and beta (tentatively designated from differences in their retention time) were determined as R- and S-forms, respectively. For both diastereomers, their NMR-determined duplex structure showed that trans-azobenzene intercalates between base pairs, because distinct NOEs were observed between the protons of azobenzene and those of the adjacent base pairs, such as with the imino protons and methyl protons of thymine. The melting temperatures of both duplexes were higher than that of the corresponding native duplex, which contained no azobenzene residue, due to the intercalated trans-azobenzene stabilizing the duplex by a stacking interaction. Between these two diastereomers, differences in T(m) were also found: the melting temperature of the R-form duplex (alpha-isomer) was higher than that of the S-form (beta-isomer). On the basis of the NMR-determined structure, this difference was attributed to the fact that the S-form (beta isomer) causes more stress forming the duplex than does the R-form (alpha isomer) due to disturbances of the right-hand helix.     

Ein metrischer Raum,der eine Verallgemeinerung des Finslerschen Raumes ist

Ohne Zusammenfassung     

Dechlorination of poly(vinyl chloride) using NaOH in ethylene glycol under atmospheric pressure

A solution of NaOH dissolved in ethylene glycol (EG) was effective in the dechlorination of poly(vinyl chloride) (PVC) at atmospheric pressure. The degree of dechlorination increased with increasing temperature, reaching a maximum of 97.8% at 190 °C. The dechlorination proceeded under chemical control and exhibited first-order kinetics with an apparent activation energy of 170 kJ mol⁻¹. The apparent rate constant for dechlorination in 1.0 M NaOH/EG was approximately 150 times greater than that in 1.0 M NaOH/H₂O. In addition, dechlorination was faster at atmospheric pressure in NaOH/EG than under high pressure in NaOH/H₂O. The dechlorination reaction occurs via a combination of E2 and S_N2 mechanisms.     

Improved determination of milk oligosaccharides using a single derivatization with anthranilic acid and separation by reversed-phase high-performance liquid chromatography

An improved analytical scheme for human milk neutral oligosaccharides determination was developed, in which, the oligosaccharides were pooled in two fractions (pools 1 and 2) after gel filtration, and then were quantitatively derivatized with a single fluorescent reagent, 2-anthranilic acid. Separation was by reversed-phase HPLC on an ODS-100Z column with a mobile phase of 50 mM ammonium acetate pH 4.0 and 150 mM citrate buffer pH 4.5 and monitored by a fluorescence detector at 360 nm excitation and 425 nm emission wavelengths. The method improved on the separation of neutral tetra- and hexa-saccharide isomers, namely, lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNnT) as well as of lacto-N-difucohexaose I (LNDFH I) and lacto-N-difucohexaose II (LNDFH II). The separation of trisacccharide isomers, 3-fucosyllactose (3-FL) and 2′-fucosyllactose (2′-FL) was also successful. Limits of detection and quantification were in the range of 1–10 ng/l and 2–30 ng/l, respectively. The methods’ accuracy was good with its precision at <20% RSD and <1% RSD, respectively, for oligosaccharide concentration and retention time. The recoveries were in the range of 80–100%. This method was successfully applied to the separation and determination of representative neutral oligosaccharide contents in Samoa women milk.     

Dechlorination behaviour of flexible poly(vinyl chloride) in NaOH/EG solution

Flexible poly(vinyl chloride) (PVC) was found to be dechlorinated in NaOH/ethylene glycol (EG) solution at moderate temperature and at atmospheric pressure. The degree of dechlorination increased over time with all particle sizes and with decreasing particle size. Decreased particle size resulted in an increased effective surface area, increasing the contact between the material and OH⁻ in the NaOH/EG solution, which contributed to the high degree of dechlorination. The dechlorination of flexible PVC in NaOH/EG solution was expressed as a first-order reaction and proceeded under chemical reaction control. Diisononyl-phthalate (DINP) in the flexible PVC powder decomposed readily into phthalic acid and isononyl alcohol in a short time. For the dechlorination of the flexible PVC, the substitution (S_N2) of chloride by the hydroxyl group was considered to be preferential to the elimination (E2) of hydrogen chloride.     

Asymmetric synthesis of (alphaR)-polyfluoroalkylated prolinols based on the perfluoroalkyl-induced highly stereoselective reduction of perfluoroalkyl N-Boc-pyrrolidyl ketones

Reduction of the obtained chiral (S)- tert-butyl 2-(perfluoroalkanoyl)pyrrolidine-1-carboxylate with sodium borohydride or lithium aluminum hydride proceeded smoothly to give the corresponding (S)- tert-butyl 2-((R)-perfluoro-1-hydroxyalkyl)pyrrolidine-1-carboxylate in yields of 73-97% with excellent diastereoselectivities (up to >98% de), compared with the reduction of nonfluorinated (S)-tert-butyl 2-pentanoylpyrrolidine-1-carboxylate.     

Large-volume sample on-line concentration of angiotensins in non-aqueous capillary electrophoresis

A single step on-line concentration and separation method for peptides in non-aqueous capillary electrophoresis was developed. ACN containing 50 mM tetraethylammonium perchlorate was used as the electrophoretic medium; angiotensins I-IV were separated as a result of the differences in the magnitudes of their interactions with perchlorate anions. When the sample solution (ACN containing 0.5% trifluoroacetic acid and angiotensins) was injected as a large-volume plug, the analytes were concentrated at the inlet end of the capillary by both sweeping and stacking mechanisms; the separation procedure then started automatically without any operations such as polarity change. It was found that the concentration of analytes, injection period, and concentration of tetraethylammonium perchlorate in the electrophoretic medium were important factors for both separation and concentration efficiencies. The angiotensins were concentrated and separated with the large-volume injection of up to 80% of the effective capillary length.     

Synthesis of Hydrotalcite using Magnesium from Seawater and Dolomite

Abstract

Three methods of synthesizing hydrotalcite(HT) have been developed using magnesium from seawater and dolomite(MgCa(CO₃)₂). In the first process, 1.0M Na₂CO₃solution was added to calcium ion free artificial seawater containing AlCl₃ with an initial Mg/Al molar ratio of 2.0～3.7 until a pH of 10 was obtained. The solution was then continuously stirred for Ih at 60°C. CO₃ ^2--HT was precipitated as a single phase, and the initial Mg/Al molar ratio, which each recovery of Mg²⁺and Al³⁺ from the solution was above 98%, was 2.0–2.3. In the second process, a Ca(OH)₂ slurry was added to artificial seawater containing AlCl₃ with an initial Mg/Al molar ratio of 1.0～5.0 until a pH of 10.5 was obtained, and then was stirred for Ih at 60°C. HT was also precipitated as a single phase with initial Mg/Al molar ratio 2.0～4.0. The initial Mg/Al molar ratio, which each recovery of Mg²⁺ and Al³⁺ from the solution was above 98%, was 2.2～3.3, but SO₄ ^2- and Cl^? were contained in the precipitated HT. When HT was produced using initial Mg/Al molar ratio of 3.0 at 25°C, SO₄ ^2- and Cl^?in the HT were ion-exchanged with CO₃ ^2- in a 0.05M Na₂CO₃solution for 24h at 25°C, and SO₄ ^2- and Cl^? content of the HT were decreased to 0.5 and 0.05wt%, respectively. In the third process, dolomite calcined at 1000°C was added to an AlCl₃ solution with an initial Mg/Al molar ratio of 1.0～2.0, and the solution was stirred for 1～4h at 25～90°C. HT was precipitated with the smallest amount of MgO and Mg(OH)₂ when the initial Mg/Al molar ratio was 1.5 and the solution was stirred for 4h at 90°C.     

Reverse genetic studies of mitochondrial DNA-based diseases using a mouse model

In the situation that it would not be able to produce model animals for mitochondrial diseases caused by mitochondrial DNA (mtDNA) with pathogenic mutations, we succeeded in generating mice with pathogenic deletion mutant mtDNA (DeltamtDNA), named "mito-mice", by direct introduction of mitochondria with DeltamtDNA into mouse zygotes. In the mito-mice, accumulation of DeltamtDNA induced mitochondrial respiration defects in various tissues, resulting in mitochondrial disease phenotypes, such as low body weight, lactic acidosis, ischemia, myopathy, heart block, deafness, male infertility, and renal failure. Thus, mito-mice are the first model animal for mtDNA-based diseases, and the mice could be valuable for understanding precise pathogeneses and testing therapies of mitochondrial diseases. In the present review, we summarized reverse genetic studies using the mito-mice.(Communicated by Takao SEKIYA, M.J.A.).