Chiral separation of acidic drug components by open tubular electrochromatography using avidin immobilized capillaries

Avidin was immobilized covalently onto the inner surface of fused silica capillaries as a stationary phase in an open tubular capillary electrochromatography (OT-CEC) for chiral separations. The modification was attained by a combination of glutaraldehyde with both an amino-silylated fused silica surface and avidin using a Schiff base formation reaction. This method couples the advantage of high efficiency and small consumption of a chiral selector with the possibility of UV detection without limitations of protein absorption. In addition, the prepared capillary was stable for 50 days with over 100 runs. To evaluate the electrochromatographic performance of the prepared capillaries, the chiral separation of abscisic acid and arylpropionic acids were investigated. Effects of the modification condition of protein, pH of running buffer, and an organic modifier on the enantioseparation were also investigated. In addition, the avidin immobilized capillary was employed for the selective chiral analysis with an electrospray ionization mass spectrometry (ESI-MS) detection scheme.     

Analysis of arsenic compounds by capillary electrophoresis using indirect UV and mass spectrometric detections

CE with indirect UV and mass-spectrometric detection was used for the simultaneous determination of arsenic acid (As(V)), arsenous acid (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (TMA(+)), arsenobetaine (AB), and arsenocholine (AC). In the CE-indirect UV analysis, a baseline separation of arsenic species was successfully achieved by using a basic background solution (BGS) for anions and an acidic BGS for cations, respectively. The LOD values in CE-indirect UV for the individual analytes were 7.8, 12.5, 7.8, 12.5, 62.5, 125, 250, and 62.5 ppm, respectively. To achieve sensitive and selective analysis, CE coupled with ESI-MS was applied to the determination of arsenic compounds. The organic arsenic species were successfully separated with a higher sensitivity by CE-MS using the acidic BGS. The LODs in CE-MS for MMA, DMA, TMAO, TMA(+), AB, and AC were 1.0, 0.1, 0.01, 0.1, 0.01, and 0.01 ppm, respectively. In contrast, the analysis of inorganic arsenic species (As(V) and As(III)) resulted in a lower detectability in CE-MS compared to that obtained with the CE-indirect UV analysis. However, the speciation of eight arsenics by CE-MS was successfully achieved in a single run by switching the ESI polarity during MS detection.     

Synthetic Studies of the Zoanthamine Alkaloids: The Total Syntheses of Norzoanthamine and Zoanthamine

Highly effective : We report herein the first and highly efficient total syntheses of norzoanthamine and zoanthamine in full detail, which involves stereoselective synthesis of the requisite triene for an intramolecular Diels–Alder reaction via three‐component coupling reactions, the intramolecular Diels–Alder reaction, and subsequent crucial bis‐aminoacetalization as the key steps.

     

A Bijection Theorem for Domino Tilings with Diagonal Impurities

We consider the dimer problem on a planar non-bipartite graph G, where there are two types of dimers one of which we regard as impurities. Computer simulations reveal a reminiscence of the Cheerios effect, that is, impurities are attracted to the boundary, which is the motivation to study this particular graph. Our main theorem is a variant of the Temperley bijection: a bijection between the set of dimer coverings and the set of spanning forests with certain conditions. We further discuss some implications of this theorem: (1) the local move connectedness yielding an ergodic Markov chain on the set of all possible dimer coverings, and (2) a rough bound for the number of dimer coverings and that for the probability of finding an impurity at a given edge, which is an extension of a result in (Nakano and Sadahiro in ).     

Novel Tb(III) complexes with two different structures of phosphine oxides and their properties

Novel Tb(III) complexes with two different structures of phosphine oxide ligands and three β-diketonates were synthesized. Characteristic of the excitation spectra mainly depend on the substituents of β-diketonates, and remarkable correlation among molecular structures, maximum wavelengths and emission intensity could be found. Namely, the shorter the maximum wavelengths when electron-donating groups are substituted in β-diketonates, the larger the emission intensity. These results were explained on the basis of extent of back energy transfer from excited Tb(III) ions to the ligand. From the analysis of the branching ratio of emission spectra, that is defined as the ratio of the intensity of the electric-dipole transition to the magnetic-dipole transition, complex 2 with β-diketonates having small substituent (methyl group) has more asymmetric ligand fields than others. It was found that introduction of two different phosphine oxide was effective for increasing solubility of Tb(III) complexes.     

Quantum phase transitions in a frustration-free spin chain based on modified Motzkin walks

Area law violations for entanglement entropy in the form of a square root has recently been studied for one-dimensional frustration-free quantum systems based on the Motzkin walks and their variations. Here, we further modify the Motzkin walks using the elements of a symmetric inverse semigroup as basis states on each step of the walk. This change alters the number of paths allowed in the Motzkin walks and by introducing an appropriate term in the Hamiltonian with a tunable parameter we show that we can jump from a state that violates the area law logarithmically to a state that obeys the area law providing an example of quantum phase transition in a one-dimensional system.     

Fully automated online multi-dimensional protein profiling system for complex mixtures

For high throughput proteome analysis of highly complex protein mixtures, we have constructed a fully automated online system for multi-dimensional protein profiling, which utilizes a combination of two-dimensional liquid chromatography and tandem mass spectrometry (2D-LC-MS-MS), based on our well-established offline system described previously [K. Fujii, T. Nakano, T. Kawamura, F. Usui, Y. Bando, R. Wang, T. Nishimura, J. Proteome Res. 3 (2004) 712]. A two-valve switching system on a programmable auto sample injector is utilized for online two-dimensional chromatography with strong cation-exchange (SCX) and reversed-phase (RP) separations. The SCX separation is carried out during the equilibration of RP chromatography and the entire sequence of analysis was performed under fully automated conditions within 4 h, based on six SCX fractionations, and 40 min running time for the two-dimensional RP chromatography. In order to evaluate its performance in the detection and identification of proteins, digests of six standard proteins and yeast 20S proteasome have been analyzed and their results were compared to those obtained by the one-dimensional reversed-phase chromatography system (ID-LC-MS-MS). The 2D-LC-MS-MS system demonstrated that both the number of peptide fragments detected and the protein coverage had more than doubled. Furthermore, this multi-dimensional protein profiling system was also applied to the human 26S proteasome, which is one of the highly complex protein mixtures. Consequently, 723 peptide fragments were identified as 31 proteasome components, together with other coexisting proteins in the sample. The identification could be comprehensively performed with a 63% sequence coverage on an average, and additionally, with modifications at the N-terminus. These results indicated that the online 2D-LC-MS-MS system being described here is capable of analyzing highly complex protein mixtures in a high throughput manner, and that it would be applicable to dynamic proteomics.     

Intense femtosecond pulse shaping using a fused-silica spatial light modulator

We present the design concept of a setup of a pulse shaper to be used for high-power femtosecond lasers. The pulse shaper is constructed from a high-damage threshold fused-silica spatial light modulator and a 4-f optical system based on the design concept to avoid optical damage. We have successfully demonstrated a pulse compression of 20 fs, 5 mJ pulses obtained from a 1 kHz repetition rate Ti:sapphire chirped pulse amplification system at an average power of 5 W.     

Magnetic properties of Europium-graphite intercalation compound C6Eu

An ordered state with a complex magnetic structure has been observed below 4CK. The magnetization for H ⊥ c (c; the c-axis) shows a field-induced phase transition from a small magnetic moment state ( ～ 0.6μ_B) at lower fields to a larger moment one ( 2.2 - 2.5μ_B) above 25kG. The transition field depends on temperature and is found to be 5 - 2kG. The magnetization for H//c has only a sublinear field dependence. Above 40K the magnetic susceptibility obeys the Curie-Weiss law with θ = +1.3K and the molar Curie constant C_m = 6.78, which suggests that Eu ion is divalent in C₆Eu.