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.     

Fliplike motion in the thalidomide dimer: Conformational analysis of (R)-thalidomide using vibrational circular dichroism spectroscopy

The dynamic fliplike motion in the (R)-thalidomide dimer has been reported for the first time. The vibrational circular dichroism (VCD) spectrum of (R)-thalidomide in DMSO-d6 indicates the characteristic nu(CO) bands with opposite signs and reflects the structural property of the equatorial configuration of the phthalimide ring. On the other hand, the VCD spectrum of (R)-thalidomide in CDCl3 exhibits a different pattern of nu(CO) bands and suggests the fliplike motion in dimer forms. This novel insight for the dimer forms would be helpful for the understanding of the structure-activity relationship for thalidomide.     

Determination of vitamin K homologues by high-performance liquid chromatography with on-line photoreactor and peroxyoxalate chemiluminescence detection

A sensitive and highly selective high-performance liquid chromatography (HPLC) method was developed for the determination of vitamin K homologues including phylloquinone (PK), menaquinone-4 (MK-4) and menaquinone-7 (MK-7) in human plasma using post-column peroxyoxalate chemiluminescence (PO-CL) detection following on-line ultraviolet (UV) irradiation. The method was based on ultraviolet irradiation (254 nm, 15 W) of vitamin K to produce hydrogen peroxide and a fluorescent product at the same time, which can be determined with PO-CL detection. The separation of vitamin K by HPLC was accomplished isocratically on an ODS column within 35 min. The method involves the use of 2-methyl-3-pentadecyl-1,4-naphthoquinone as an internal standard. The detection limits (signal-to-noise ratio = 3) were 32, 38 and 85 fmol for PK, MK-4 and MK-7, respectively. The recoveries of PK, MK-4 and MK-7 were greater than 82% and the inter- and intra-assay R.S.D. values were 1.9-5.4%. The sensitivity and selectivity of this method were sufficient for clinical and nutritional applications.     

Asymmetric catalysis via dynamic substrate/ligand/rare earth metal conglomerate

A highly enantio- and diastereoselective catalytic asymmetric Mannich-type reaction of alpha-cyanoketones and N-Boc imines promoted by an amide ligand/Sc(OiPr)3 catalyst is described. The similar reaction outcome is obtained with/without precomplexation of catalyst, suggesting that reaction components in a non-ordered conglomerate mixture orchestrate to form an ordered transition state during the reaction. Spectroscopic data and Eyring plot are consistent with this assumption.     

Transient vibronic structure in ultrafast fluorescence spectra of photoactive yellow protein

The ultrafast photo-induced dynamics of wild-type photoactive yellow protein and its site-directed mutant of E46Q in aqueous solution was studied at room temperature by femtosecond fluorescence spectroscopy using the optical Kerr-gate method. The vibronic structure appears, depending on the excitation photon energy, in the time-resolved fluorescence spectra just after photoexcitation, which winds with time and disappears on a time scale of sub-picoseconds. This result indicates that the wavepacket is localized in the electronic excited state followed by dumped oscillations and broadening, and also that the initial condition of the wavepacket prepared depending on the excitation photon energy affects much the following ultrafast dynamics in the electronic excited state.     

Hydrophobic and metal coordination interacted architecture based on p-tert-butylthiacalix[4]arene–potassium complex and its vapor absorption capability

Single-crystal X-ray diffraction studies of [K(1·3H)]·2MeOH complex obtained from p-tert-butylthiacalix[4]arene (1·4H) with KH, which shows two dimer formations. One of the dimers is formed by a hydrophobic interaction between each tert-butyl group of 1·3H and the cavity of another 1·3H in the crystalline state. The other dimer made metal coordination SK(O,S,O) between neighboring 1·3H and potassium ion. In the overall structure, this complex indicates non-porous structure and the adsorption capabilities toward gaseous organic molecules.     

A simple and rapid CZE method for the analysis of mycophenolic acid and its phenol glucuronide metabolite in human serum

A simple and rapid capillary electrophoretic method was developed for simultaneous determination of mycophenolic acid and its metabolite, phenol glucuronide, in human serum. The sample preparation in the proposed method required only the precipitation by acetonitrile. Separation was performed by capillary zone electrophoresis using 75 mM phosphate buffer (pH 7.5) as running buffer, an applied voltage of 10 kV, and UV detection at 217 nm. Each serum sample analysis was completed within 15 min. The optimized method demonstrated good performance concerning specificity, linearity (r>0.9955), accuracy (95.9-113%), precision (<6.4%) and enough sensitivity for therapeutic drug monitoring. This method was successfully applied to measurements of mycophenolic acid and mycophenolic acid glucuronide in renal transplant patient samples and was a useful alternative to high-performance liquid chromatography-based methods.     

High-performance thin-layer chromatography/mass spectrometry for rapid analysis of neutral glycosphingolipids

Direct coupling of high-performance thin-layer chromatography (HPTLC) to matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MS) was shown to be a reliable and reproducible method to obtain structural information and fundamental properties of glycosphingolipids (GSLs). We report a protocol for the preparation of neutral GSL extracts from mouse tissues and demonstrate the applicability of HPTLC/MS to these preparations. The protocol consists of lipid extraction and ion exchange chromatography followed by a mild alkaline treatment and a reversed-phase cartridge extraction. Possible structures for each GSL are proposed based on HPTLC/MS analyses. This fast and simple method can be used to screen neutral GSL extracts obtained from tissues and cells without isolation and purification into individual GSLs.     

An Aqueous Redox Flow Battery Using CO2 as an Active Material with a Homogeneous Ir Catalyst**

For the application of CO₂ as an energy storage material, a H₂ storage system has been proposed based on the interconversion of CO₂ and formic acid (or formate). However, energy losses are inevitable in the conversion of electrical energy to H₂ as chemical energy (≈70 % electrical efficiency) and H₂ to electrical energy (≈40 % electrical efficiency). To overcome these significant energy losses, we developed a system based on the interconversion of CO₂ and formate for the direct storage and generation of electricity. In this paper, we report an aqueous redox flow battery system using homogeneous Ir catalysts with CO₂-formate redox pair. The system exhibited a maximum discharge capacity of 10.5 mAh (1.5 Ah L⁻¹), capacity decay of 0.2 % per cycle, and total turnover number of 2550 after 50 cycles. During charging-discharging, in situ fluorescence X-ray absorption fine structure spectroscopy based on an online setup indicated that the active species was in a high valence state of Ir^IV.