Manipulation of cell-sized phospholipid-coated microdroplets and their use as biochemical microreactors

Cell-sized water droplets coated by a phospholipid layer mimicking the inner surface of living cells were manipulated by laser tweezers and used as biochemical microreactors. The cell-sized phospholipid-coated microdroplets (CPMDs) consisted of a water droplet in mineral oil with a diameter of 1-100 microm and coated by 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine. We monitored the time development of biochemical reactions in a single CPMD obtained after the controlled fusion of two CPMDs containing a substrate and an enzyme, respectively. We present results on two enzymatic reactions: calcein production in the presence of esterase and green fluorescence protein expression.     

Vibrational spectra of zinc halide complexes with trimethylphosphine oxide

The Raman and IR spectra are reported for the complexes ZnCl₂.2TMPO, ZnBr₂.2TMPO and ZnI₂.2TMPO. The observed frequencies for polycrystalline samples are assigned on the basis of a C_3v structure for the TMPO ligand and a C_2y structure for the ZnX₂O₂ skeletal fundamentals. To discuss the coordination effects of TMPO, the ligand vibrations are compared with those of free TMPO and the skeletal vibrations with those of acetonitrile complexes. Using the ratios of G matrix elements and of observed frequencies for symmetric and asymmetric Zn-X stretching modes, the ZnX₂O₂ skeletal structures are found to be tetrahedral.     

On the third fundamental band of Li+ translational vibration in lithium hydrogen oxalate monohydrate

The third Li⁺ translational mode of lattice vibration of lithium hydrogen oxalate monohydrate has been assigned to the band at about 383/360 cm^–1 taking the characteristic⁶Li/⁷Li isotope band shifts into consideration.

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Über die Zuordnung einer der drei translatorischen Li⁺-Moden in Lithiumhydrogenoxalat-Monohydrat (Kurze Mitteilung)

Zusammenfassung Es wurden die IR-Spektren der Li- und H-isotopen Lithiumhydrogenoxalat-Monohydrate bei 100 K und 300 K gemessen. Einer der drei translatorischen Moden wird einer Bande zugeordnet, die bei Berücksichtigung der⁶Li/⁷Li Isotopenverschiebung bei 383/360 cm^–1 auftritt.

     

An homologous series of benzodiazepine retention index standards for gas chromatography

An homologous series of benzodiazepine retention index standards (the R-series) has been synthesized and the gas chromatographic behavior of the series investigated on NB-54 and NB-1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R-series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R-series method was found to be generally better than that of the two other methods in both long- and short-term studies.     

Dissociation and IVR pathways for the CF3H(H2O)3 cluster

Classical trajectory simulations are used to study the intramolecular dynamics of isolated CF₃H and the CF₃H(H₂O)₃ cluster, by either exciting the CH stretch local mode to then=6 level or by adding an equivalent amount of energy to an OH stretch normal mode. Energy transfer from the CH local mode is statistically the same for CF₃H(H₂O)₃ as for isolated CF₃H, and agrees with previous experimental studies. Clusters excited with 6 quanta in the CH local mode are remarkably stable. Though the CF₃H-(H₂O)₃ intermolecular potential is only 1.5 kcal/mol, only 1 of 26 clusters excited with 6 quanta in the CH local mode dissociate within 10 ps. The absorption linewidth for the CH local mode in CF₃H(H₂O)₃ is related to IVR within CF₃H and not to the unimolecular lifetime of the cluster. When an OH stretch normal mode of the cluster is excited, energy transfer to CF₃H is negligible and nearly one half of the clusters dissociate within 10 ps.     

O + C<Subscript>2</Subscript>H<Subscript>4</Subscript> potential energy surface: excited states and biradicals at the multireference level

The focus of this study is to understand the multiconfigurational nature of the biradical species involved in the early reaction paths of the oxygen plus ethylene PES. In previous work (J Phys Chem A 113, 12663, 2009), the lowest-lying O(³P) + C₂H₄ PES was extensively explored at the MCSCF, MRMP2, and MR-AQCC levels of theory. In the current work, ground and excited, triplet- and singlet-state reaction paths for the initial addition of oxygen to ethylene were found at the MCSCF and MRMP2 levels along with five singlet pathways near the ^·CH₂CH₂O^· biradical at the MCSCF, MRMP2, and CR-CC(2,3) levels. One of these five paths can lead to the CH₂CO + H₂ products from CH₃CHO rather than from the ^·CH₂CH₂O^· biradical, and this pathway was investigated with a variety of CAS sizes. To provide further comparison between the MRMP2 and CR-CC(2,3) levels, MR-AQCC single-point energies and optimizations were performed for select geometries. After the initial exploration of this region of the surface, the lowest singlet–triplet surface crossings were explicitly determined at the MCSCF level. Additional MRMP2 calculations were performed to demonstrate the limitations of single-state perturbation theory in this biradical region of the PES, and SO-MCQDPT2 single-point energies using SA MCSCF were calculated on a grid of geometries around the primary surface crossing. In particular, these calculations were examined to determine a proper active space and a physically reasonable number of electronic states. The results of this examination show that at least four states must be considered to represent this very complex region of the PES.     

Specific assay for endotoxin using immobilized histidine, Limulus amoebocyte lysate and a chromogenic substrate.

The Limulus amoebocyte lysate (LAL) test is inhibited or enhanced by many substances. In order to overcome this problem, a specific endotoxin assay method using a membrane filter unit, a chromogenic LAL reagent, and immobilized histidine (which is a specific adsorbent for endotoxins) was developed. Endotoxins are quantitatively adsorbed on immobilized histidine. The adsorbed endotoxins are separated from LAL-inhibiting or -enhancing substances by the membrane filter unit, and their activities are directly assayed with the LAL reagent in a filter cup without any inhibition or enhancement. The reproducibility and the accuracy of this method are high. This new endotoxin assay method using immobilized histidine can be used for the determination of endotoxins in a solution containing LAL-inhibiting or -enhancing substances such as amino acids and antibiotics, as an alternative to the more common gel-clot technique.     

Adduct formed by chromium trioxide and zwitterionic quinolinic acid

Chromium trioxide forms an adduct with zwitterionic quinolinic acid. The structure of the product was found to be (quinolinium-3-carboxylato-O)trioxidochromium(VI), determined by single-crystal X-ray diffraction methods. To evaluate the bonding properties of the compound, its structure was optimized at the B3LYP/6-311G* level of theory. The electronic characteristics were investigated by topological methods applied to the total charge density in various model compounds including the title compound, title compound with a HF molecule presenting a hydrogen bonding and anionic moiety. Calculated aromaticity indices indicate that the quinolinic rings tend to conserve their degree of aromaticity against hydrogen bonding. However, when there is hydrogen bonding involving an N-H bond or when the quinolinium zwitterion is deprotonated, there are clear changes in the interaction between chromium trioxide and the quinolinic moiety.