Supercritical carbon dioxide extraction of ubiquinones and menaquinones from activated sludge

Supercritical CO2 (scCO2) extraction, with methanol as modifier, was applied to the determination of ubiquinones and menaquinones in activated sludge. Four ubiquinones and 12 menaquinones species were identified based on retention time and UV spectrum in 0.1g dried activated sludge. The optimum extraction conditions were at a pressure of 25 MPa, a temperature of 55 degrees C, and 10% (v/v) methanol for 15 min. At this condition, the concentrations of extracted ubiquinones and menaquinones were found to be 0.181 and 0.326 micromol/g-dry-cell, respectively. The results were comparable with those obtained by organic solvent extraction based on diversity and dissimilarity indices. Furthermore, the method was evaluated in term of repeatability, which resulted in an RSD of < or =10%. The experimental results have demonstrated the technique to be simple, fast, and with less consumption of organic solvents. This work shows the potential application of supercritical CO2 extraction to microbial community analysis using quinone profile.     

Mass selective ejection by axial resonant excitation from a linear ion trap

We describe a new mass selective ejection method from a linear ion trap, which we call axial resonant excitation (AREX). A set of vane lenses are inserted between each quadrupole rod to produce electrostatic potential that is approximately harmonic along the central axis of the quadrupole field. After ions with specific m/z are resonantly oscillated in the axial direction, the ions are mass selectively ejected in the axial direction. At a high scan rate of 11 Th/ms, AREX achieved a high ejection efficiency of more than 60%, which is more than three times higher than a conventional mass selective axial ejection method from a linear trap using fringing field.     

Practical method for the synthesis of (R)-homopipecolinic acid and (R)-homoproline esters from ω-chloroalkanoic acids and available chiral amines

A practical synthesis of (R)-homopipecolinic acid methyl ester 1 and (R)-homoproline methyl ester 2 was performed utilizing (i) a direct intramolecular cyclization of ω-chloro-β-enamino esters 11 and 12, which were prepared from available (S)-1-phenylethylamine or (S)-1-(1-naphthyl)ethylamine and ω-chloro-β-keto esters 5 and 10, respectively and (ii) a highly diastereoselective NaBH₄ reduction followed by hydrogenolysis. The present method is a short-step process using inexpensive and readily available substrates and reagents with fewer wasted materials.     

Stereocontrolled synthesis of the IJK ring segment of yessotoxin

A stereocontrolled synthesis of the IJK ring segment of yessotoxin is described. Cyclization of 11 mediated by SmI₂ gave the IJ ring system 12 as the sole product. Construction of the K ring moiety was performed by the acid catalyzed cyclization of epoxy alcohol 20 to afford the IJK ring segment in a highly stereocontrolled manner.     

Stereochemistry of pteriatoxins A, B, and C

The C34 and C2' stereochemistry of pteriatoxins A-C has been established. The availability of all the stereoisomers via total synthesis has played an indispensable role.     

Selective ion-binding by protein probed with the 3D-RISM theory

Cations (Ca2+, Na+, K+) selectively bound by human lysozyme and its mutants are probed by the 3D-RISM theory, a statistical mechanics theory of liquids.     

Syntheses and characterization of oxygen/sulfur-bridged incomplete cubane-type clusters, [Mo3S4Tp3]+ and [Mo3OS3Tp3]+, and a mixed-metal cubane-type cluster, [Mo3FeS4ClTp3]. X-ray structures of [Mo3S4Tp3]Cl, [Mo3OS3Tp3]PF6, and [Mo3FeS4ClTp3

The reaction of [Mo3S4(H2O)9]4+ (1) with hydrotris(pyrazolyl)borate (Tp) ligands produced [Mo3S4Tp3]Cl x 4 H2O ([3]Cl x 4 H2O) in an excellent yield. An X-ray structure analysis of [3]Cl x 4 H2O revealed that each molybdenum atom bonded to the Tp ligand. We report four salts of 3, [3]Cl x 4 H2O, [3]tof x 2 H2O, [3]PF6 x H2O, and [3]BF4 x 2 H2O in this paper. The solubility and stability of the chloride salt in organic solvents differ completely from those of the other salts. We have also prepared a new compound, [Mo3OS3Tp3]PF6 x H2O ([4]PF6 x H2O), via the reaction of [Mo3OS3(H2O)9]4+ (2) with KTp in the presence of NH4PF6. All the molybdenum atoms bonded to Tp ligand. 1H NMR signals corresponding to nine protons bonded to three pyrazole rings in one Tp were observed in a spectrum (at 253 K) of [3]BF4 x 2 H2O. It shows that cluster 3 has a 3-fold rotation axis in CD2Cl2 solution. Twenty-one 1H NMR signals corresponding to twenty-seven protons bonded to nine pyrazole rings in three Tp ligands were observed in a spectrum (at 233 K) of [4]PF6 x H2O; obviously, 4 has no 3-fold rotation axis, in contrast to 3. The short CH...mu3S distance caused large upfield chemical shifts in the 1H NMR spectra of 3 and 4. The reaction of 3 with metallic iron in CH2Cl2 produced [Mo3FeS4XTp3] (X = Cl (5), Br (6)). X-ray structure analysis of 5 has revealed the existence of a cubane-type core Mo3FeS4. Complex 3 functions as a metal-complex ligand for preparing a novel mixed-metal complex even in nonaqueous solvents. The cyclic voltammogram of 5 shows two reversible one-electron couples (E(1/2) = -1.40 and 0.52 V vs SCE) and two irreversible one-electron oxidation processes (E(pc) = 1.54 and 1.66 V vs SCE).     

Structures of 1-(arylseleninyl)naphthalenes: O, G, and Y dependences in 8-G-1-[p-YC6H4Se(O)]C10H6

Structures of 8-G-1-[p-YC6H4Se(O)]C10H6 [1 (G = H), 2 (G = F), 3 (G = Cl), and 4 (G = Br): Y = H, OMe, OCH2Ph, t-Bu, Me, Cl, and NO2] and (1-C10H7)2SeO (5) are investigated by the X-ray crystallographic analysis. Structures of 1 are all A with regard to the naphthyl group (1 (A)), where the Se-C(Ar) and Se-O bonds are perpendicular to and parallel to the naphthyl plane, respectively. Those of 2-4 are also A. Since structures of 8-G-1-(p-YC6H4Se)C10H6 [7 (G = F), 8 (G = Cl), and 9 (G = Br)] are all B, the results exhibit that B of 7-9 change dramatically to A of 2-4 with the introduction of O atoms. The factor to determine the A structures of 1-4 by O is called O dependence. The origin of the O dependence is the nonbonded np(O)- - -pi(Nap) interaction, which results in CT from np(O) to pi(Nap) since O in 1-4 is highly electron rich due to the polar Se+=O- bond and pi(Nap) acts as an acceptor. There are two types of np(O)'s, npy(O) and npz(O), if the directions of the Se-O bond and the p-orbitals of pi(Nap) are taken in the x- and z-axes, respectively. Double but independent np(O)- - -pi(Nap) interactions in 5 lead to 5 (AA). The conformation of the p-YC6H4Se group in 1 changes depending on Y (Y dependence), although the effect is not strong. The Y dependence is explained on the basis of the magnitude of CT of the np(O)-->pi(Ar) type in 1, in addition to the np(O)- - -pi(Nap) interaction. The structure around the Se=O group in 1 is close to that of 5 (AA), if the accepting ability of the p-YC6H4Se group is similar to that of the naphthyl group. A of 2-4 are further stabilized by the np(G)- - -sigma(Se-O) 3c-4e interactions, which are called G dependence. QC calculations performed on the methyl analogues of 1-4 (11-14, respectively) reproduced the observed structures, supported the above discussion, and revealed the energy profiles. The energy-lowering effect of the O dependence would be close to the G dependence of the nonbonded n(Br)- - -sigma(Se-O) 3c-4e interaction in 14 if the steric repulsion between Br and Se is contained in the G dependence. The value is roughly predicted as 20 kJ mol(-1). The structures of 1-5 are well explained by O, G, and Y dependences.     

In situ generation of 3,3,3-trifluoropropanal and its use for carbon-carbon bond-forming reactions

The DIBAL reduction of 2-phenylethyl 3,3,3-trifluoro-2-methylpropionate 2 at -78 degrees C afforded the aluminum acetal 3, and this intermediate, on worming up to 0 degrees C, was found to slowly decompose into the corresponding aldehyde 4, which smoothly reacted with appropriate nucleophiles in a one-pot manner in good to excellent yields with up to 93% diastereoselectivity.     

Ultra-slim laminated capillary array for high-speed DNA separation

We developed a new kind of capillary array for electrophoresis by using the numerical-control (NC) wiring technique conventionally used to produce printed-circuit boards. Laminating two polyimide sheets after laying cylindrical capillaries between them according to designed geometries, we fabricated a 16-lane laminated capillary array (LCA) 9.9 cm long, 7.2 cm wide, and 0.5 mm thick in which the effective length of all capillaries was only 10.9 cm. This compact LCA thus had separation columns as short as those in capillary array electrophoresis chips fabricated by lithography techniques. Like conventional capillary arrays, it also enabled pipetting-less direct injection of analytes from sample preparation plates. Using the LCA with LIF detection and a replaceable fluid sieving matrix, we demonstrated high-speed ssDNA fragment separations. At an electric field strength of 316 V/cm, 15 fragments ranging from 50 to 500 bases were completely separated within 5.8 min in all lanes. The lane-to-lane CV of migration time was only 0.38%, and the fragment size for which the resolution per base was 0.59 was 258 +/- 15 bases (average +/-SD).