Analysis of protein-protein interactions with a multi-capillary electrophoresis instrument

Protein-protein interactions were analyzed by zone electrophoresis of premixed equilibrium mixtures of a fluorescence-labeled protein at a constant concentration and unlabeled protein at a variety of concentrations using a 96-CE instrument equipped with a LIF detector. The interactions between labeled-con A versus succinylated ovalbumin, labeled-trypsin versus four proteinaceous trypsin inhibitors and labeled-insulin versus seven anti-insulin monoclonal antibodies were analyzed using a dual buffer system, in which a 60 mM borate-Na buffer (pH 9.35) was used as electrophoresis buffer and 60 mM MOPS-Na (pH 7.35) containing 0.1% Tween 20 was used as a sample buffer. The dual buffer system allowed fast and reproducible analyses of interactions at a physiological pH using uncoated fused-silica capillaries. The change in the mobility moment, the first statistical moment of an electropherogram on the mobility axis (Shimura, K., Uchiyama, N., Enomoto, M., Matsumoto, H., Kasai, K., Anal. Chem. 2005, 77, 564-572), of the labeled proteins were analyzed as a function of the concentration of unlabeled proteins. The dissociation constants for seven antibodies ranging from sub nanomolar to micromolar was determined based on the results of one cycle of parallel electrophoresis runs, which completed in 30 min using 20 pmol (120 ng) of labeled insulin and 5 pmol (750 ng) each of the mAb.     

Magnetic and electronic properties of palladium nanoparticles coated with pi-conjugated tetrathiafulvalenes derivative

Magnetic and electronic properties are investigated for Pd nanoparticles coated with a TTF-derivative (EDT-TTF(SCH(3))(SC(10)H(20)SH)) and octadecanethiol organic mixed monolayer. The temperature-independent spin susceptibility and spin concentration of Pd decrease upon the increasing proportion of the TTF-derivative in the organic layer. With the introduction of the derivative, the ESR broad signal originating from the interior of the Pd nanoparticles tends to vanish following the appearance of sharp signals due to the TTF radical. The presence of the TTF molecules enhances the charge transfer from the core Pd nanoparticles. The electronic state of the Pd nanoparticles changes as a consequence of the contributions of both the quantum-size effect and the charge-transfer effect between the Pd core, TTF-derivative, and alkanethiol.     

Unequivocal synthesis of (Z)-alkene and (E)-fluoroalkene dipeptide isosteres to probe structural requirements of the peptide transporter PEPT1

[reaction: see text] Described is a novel synthetic route for dipeptide isosteres containing (Z)-alkene and (E)-fluoroalkene units as cis-amide bond equivalents via organocopper-mediated reduction of gamma-acetoxy- or gamma,gamma-difluoro-alpha,beta-unsaturated-delta-lactams. The synthesized isosteres were evaluated in terms of their affinities for the peptide transporter PEPT1. trans-Amide isosteres tended to possess higher affinities for PEPT1 as compared to the corresponding cis-amide bond equivalents.     

Effect of NaOH on the solubility of fluorocarbon in alcohol–NaOH systems

We propose a dechlorination process that allows safe and environmental conversion of chlorinated fluorocarbons. Starting with dissolving a fluorocarbon in an alcohol–NaOH solution, the fluorocarbons are reacted with alcohol–NaOH solvents at room temperature and pressure. In this work, the effect of the NaOH concentration on the solubility of CCl₂F₂ (CFC-12), CH₂F₂ (HFC-32), C₂HF₅ (HFC-125), C₂H₂F₄ (HFC-134a) and C₂H₄F₂ (HFC-152a) in methanol–NaOH, ethanol–NaOH and 1-propanol–NaOH solutions was measured. The experimental salting-out effects can be explained by solvation of a few alcohol molecules on sodium ion. Setchenov coefficients were determined and found to be independent of temperature.     

Laguerre-Gaussian modes selection in diode-pumped solid-state lasers

Over the last twenty years, diode pumping of solid-state lasers has opened new prospects for the mode control and formation of Laguerre-Gaussian (LG) beams, enabling a large variety of applications. Experiments on scalar and vector LG modes selection in Nd³⁺- and Yb³⁺-doped ceramics and crystal lasers carried out at the Institute for Laser Science, Tokyo are reviewed. Selection of LG modes from low to high orders using intra-cavity elements, polarization-selective mirrors, or shaping the pump beam profile, is considered. Illustrations of record-high-order LG hollow modes, multiring modes with highly directional propagation properties, characteristics of cw and pulsed lasers with radially or azimuthally polarized beams of high polarization purity are presented. General solutions of the wave equation for the axi-symmetric electric field, which describe LG beams of various profiles, are proposed for data analysis. In parallel, a short review on LG modes selection studies carried out at other laboratories is given.     

Preparation of TiO2 thin films using water-soluble titanium complexes and their photoinduced properties

Titanium dioxide thin films were prepared by using four water-soluble titanium complexes of titanium-lactate, tartalate, malate and salicylate complex solutions. The crystalline phases detected in the films were anatase. The surface microstructures of the four film samples were different in their grain sizes. Photocatalytic decomposition activity of the four films was almost the same, but their photoinduced hydrophilicities were different. The film prepared using titanium-salicylate complex exhibited lower hydrophilic conversion rate than the other films. Grain size and stress yielded to the film are considered to be important factors on the photoinduced hydrophilicity.     

Optimization of operating conditions for desorption chemical ionization mass spectrometry

Optimization of the operating conditions for desorption chemical ionization (D/CI) mass spectrometry has been evaluated on the production of molecular ion species as well as structurally informative fragment ion species with sucrose as a main model compound. Among various parameters examined, it was found that configuration and heating rate of the emitter wire were significantly concerned with the desorption efficiency, while chamber temperature played an important role on the control of the fragmentation process rather than the desorption process. Therefore, the conditions for optimal molecular ion species are quite opposed to those for optimal fragment ion species. The former can be achieved by the use of the highest heating rate combined with the lowest chamber temperature. Under the optimal operating conditions, a 20 ng sample of sucrose is adequate for recording a clear mass spectrum with good reproducibility, where [M·NH₄]⁺ (m/z 360) is the base peak and the glycosyl ion [S·NH₃]⁺ (m/z 180) also has moderate abundance (rel. int., 40%).     

Normal Alignment of π-conjugated Oligo-acene Amphiphiles by Langmuir-Blodgett Techique

Novel type of monolayer and multilayer of normally aligned,π-conjugated system with no alkyl chain was realized consisting of oligo-acene molecules by Langmuir-Blodgett technique.     

Application of log D for the prediction of hydrophobicity in the advanced Marfey's method

In the advanced Marfey's method, the resolution between the diastereomers derivatized with 1-fluoro-2,4-dinitrophenyl-5-l-leucinamide (l-FDLA) and 1-fluoro-2,4-dinitrophenyl-5-d-leucinamide (d-FDLA) is reflected by the difference of hydrophobicity of the two functional groups at the asymmetric carbon. However, no effective method has been developed for the estimation of hydrophobicity so far. For this purpose, we introduced log D from the ACD Labs LogD and applied it to relatively simple primary amines, amino acids and secondary alcohols in the present study. It was found that the difference of the retention times (Δt_R) correlated with that of log D (Δlog D) for both diastereomers based on the obtained experimental results. Based on these results, the following procedure was proposed for the non-empirical determination of the absolute configuration of primary amines including amino acids and secondary alcohols: (1) estimate the hydrophobicity by the calculation of log D for the two substituent groups at the asymmetric carbon, (2) locate the trans-type arrangement of the two more hydrophobic substituents in the l-DLA derivative and judge the asymmetric carbon to be R or S in the trans-type that is eluted first, (3) derivatize the desired compound with l- or d-FDLA and analyze by LC/MS, and (4) compare the elution order with the prospective one and determine the absolute configuration at the asymmetric carbon. Furthermore, log D could also be used to predict the retention times of unavailable amino acids and small peptides, indicating that the combination of the advanced Marfey's method with log D would provide more reliable structural information on a mixture composed of amino acids and small peptides. The developed method is being applied to more complicated compounds.     

Chemical and morphological evolution of supported Ru nanoparticles during oxidative conversion of methane

Alumina supported Ru nanoparticles, with an initial average size of 5.8 nm, show high activity and yield to CO and H₂ at lower temperature than the conventionally prepared catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.