Norharmane: old yet highly selective dual channel ratiometric fluoride and hydrogen sulfate ion sensor

Norharmane provides a simple unexplored class of anion receptor, that allows for the ratiometric selective detection of F(-) and HSO(4)(-) ions. The presence of a strong base can easily form hydrogen bonds with the acidic hydrogen bond donor moiety and the relatively strong acid can easily protonate the basic hydrogen bond acceptor moiety, which can modulate the optical response and can detect the anions efficiently with high selectivity. In view of that, it is promising to conceive the use of these systems in various sensing applications as well as in other situations, such as anion transport and purification, where the availability of cheap and easy-to-make anion receptors, would be advantageous.     

Ultrasensitive CE for heavy metal ions using the variations in the chemical structures formed from new octadentate fluorescent probes and cationic polymers

Novel fluorescent probes have been developed for the ultratrace detection of heavy metal ions by capillary electrophoresis using laser-induced fluorescence detection. Based on a molecular design, the probes are composed of an octadentate chelating moiety, a macrocyclic DOTA (tetraazacyclododecanetetraacetic acid) and an acyclic DTPA (diethylenetriaminepentaacetic acid) frame, a spacer and a fluorophore (fluorescein). These were chosen on the basis of their ability to form kinetically inert and highly emissive complexes, and to prevent a quenching effect even with heavy and paramagnetic metal ions. Addition of a cationic polymer, polybrene, in the separation buffer provided high resolution and simultaneous detection of Ca(2+), Mg(2+), Cu(2+), Zn(2+), Ni(2+), Co(2+), Mn(2+), Cd(2+) and Pb(2+). The direct fluorescence detection of these metal ions with high sensitivity at lower ppt levels, typically 2-7 × 10(-11) M (potentially sub-ppt), was successfully achieved. While separation of anionic compounds using a counter cation ("Ion Association (IA)" mode) is typically controlled by the ion association equilibrium constants, K(ass), it was found that differences in the mobilities, μ(ep(IAC)), of the ion association complexes formed between the probe complexes and counter cations are the driving forces for separation in this new method. This suggests that each of the polybrene-probe complexes has different chemical structures among metal ions, which were able to be determined by CD spectra in this investigation. This novel separation mode was termed the "Ion Association Complex (IAC)" mode, distinct from the IA mode.     

In situ preparation of highly fluorescent dyes upon photoirradiation

Photoswitchable or photoactivatable fluorescent dyes are potentially applicable to ultrahigh density optical memory media as well as super-resolution fluorescence imaging when the dyes are highly fluorescent and have large absorption coefficients. Here, we report on highly fluorescent photochromic dyes, which are initially nonluminous in solution under irradiation with visible light but activated to emit green or red fluorescence upon irradiation with ultraviolet (UV) light. The dyes 5a-9a are sulfone derivatives of 1,2-bis(2-ethyl-6-phenyl(or thienyl)-1-benzothiophen-3-yl)perfluorocyclopentene. It was found that substitution of phenyl or thiophene rings at 6 and 6' positions of the benzothiophene-1,1-dioxide groups is effective to increase the fluorescence quantum yields of the closed-ring isomers over 0.7 and absorption coefficients over 4 × 10(4) M(-1) cm(-1). The phenyl-substituted derivatives 5a-7a undergo photocyclization reactions to produce yellow closed-ring isomers 5b-7b, which emit brilliant green fluorescence at around 550 nm (Φ(F) = 0.87-0.88) under irradiation with 488 nm light. Any absorption intensity change of the closed-ring isomers was not observed even after 100 h storage in the dark at 80 °C. The closed-ring isomers slowly returned to the initial open-ring isomers upon irradiation with visible (λ > 480 nm) light. The ring-opening quantum yields (Φ(C→O)) were measured to be (1.6-4.0) × 10(-4). When the phenyl substituents are replaced with thiophene rings, such as compounds 8a and 9a, the absorption bands of the closed-ring isomers shift to longer than 500 nm. The closed-ring isomers exhibit brilliant red fluorescences at around 620 nm (Φ(F) = 0.61-0.78) under irradiation with 532 nm light. The ring-opening reactions are very slow (Φ(C→O) < 1 × 10(-5)). The fluorescence lifetimes of these sulfone derivatives were measured to be around 2-3 ns, which is much longer than the value of the closed-ring isomer of 1,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene (τ(F) = 4 and 22 ps). The closed-ring isomer 8b in 1,4-dioxane exhibits excellent fatigue resistant property under irradiation with visible light (λ > 440 nm) superior to the stability of Rhodamine 101 in ethanol.     

Determination of proline enantiomers in honey and royal jelly by LC-UV

The chiral separation and quantification of D-proline and L-proline in honey and royal jelly were examined by LC with UV detection. Most of the endogenous compounds existing in honey, such as sugars, were removed by using SPE cartridges containing C18 and strong cation-exchange sorbent. Other components, such as primary amino acids, were also removed by two-step derivatization with o-phthalaldehyde (OPA) and 9-fluorenylmethyl chloroformate (FMOC-CI). The components that were derivatized with OPA were separated from proline with a C18 cartridge. Proline was then converted into an FMOC derivative that could be subsequently measured by LC-UV. Sufficient chiral separation of D-proline and L-proline was achieved with an LC chiral column made of a beta-cyclodextrin phase in the polar organic-phase mode. The average recoveries of D-proline and L-proline from honey and royal jelly were in the range of 81.3-98.6% (RSD of < 1.8%). When this method was applied to commercial honey and royal jelly samples, L-proline was detected at concentrations of 369-1930 microg/g, whereas D-proline was not detected.     

Preparative purification of gentamicin components using high-speed counter-current chromatography coupled with electrospray mass spectrometry

We developed a useful and preparative method based on high-speed counter-current chromatography with mass spectrometry (HSCCC/MS) to purify gentamicin C1a, C2/2a and C1 from standard powder. The analytes were purified on the HSCCC model CCC-1000 (multi-layer coil planet centrifuge) with a volatile two-phase solvent system composed of n-butanol/10% aqueous ammonia solution (50:50, v/v) and detected on an LCMS-2020EV quadrupole mass spectrometer fitted with an electrospray ionization (ESI) source system in positive ionization following scan mode (m/z 100-500). The HSCCC/ESI-MS peaks indicated that gentamicin C1a (m/z 450: [M+H](+)), C2/2a (m/z 464: [M+H](+)) and C1 (m/z 478: [M+H](+)) have the peak resolution values of 1.3 and 1.7 from 30 mg of loaded gentamicin powder. The HSCCC yielded 3.9 mg of gentamicin C1a, 12.6 mg of gentamicin C2/2a and 12.0 mg of gentamicin C1. These purified substances were analyzed by LC/MS with scan positive-mode. Based on the LC/MS chromatograms and spectra of the fractions, analytes were estimated to be over 95% pure. These gentamicin isomers of C1a, C2/2a and C1 were evaluated for their antibacterial activities. The overall results indicate that this approach of HSCCC/MS is a powerful technique for the purification of gentamicin components.     

Asymptotic stability for quasi-linear systems whose linear approximation is not assumed to be uniformly attractive

Sufficient conditions are obtained for uniform stability and asymptotic stability of the zero solution of two-dimensional quasi-linear systems under the assumption that the zero solution of linear approximation is not always uniformly attractive. A class of quasi-linear systems considered in this paper includes a planar system equivalent to the damped pendulum x′??+ h(t)x??+ sin x = 0, where h(t) is permitted to change sign. Some suitable examples are included to illustrate the main results.     

Lattice- and network-structure in plastic ice

We have investigated structural and energetic characteristics of plastic ice, which was found in a high pressure region such as 10 GPa by molecular dynamics simulation and free energy calculation. It was predicted that plastic ice intervenes between ice VII and liquid water, in which diffusion is suppressed but rotation is allowed. In the present work, the structure in plastic ice is explored from both local and global view points and focus is placed on the local arrangement, the extent of deviation from the ideal lattice position, and the hydrogen-bonded patterns. The roles of the attractive interaction and the repulsive part of Lennard-Jones potential are also examined. It is found that the higher interaction energy in plastic ice induces a large dislocation of water molecules, which eventually conducts a facile rotation. There are a large amount of hydrogen-bonds which do not orient to the tetrahedral directions. These orientational defects give rise to fusion of the two interpenetrating sublattices of ice VII leading to a plastic phase rather than defect-containing ice VII, which results in a unique network structure of the plastic ice.     

Synergic extraction of metals with α-acyl-d-camphor and optically active lewis bases

Solvent extraction of europium (III), zinc (II) cobalt (II) with α-acyl-d-camphor and optically active isomers of quinine and quinidine was studied in order to obtain information on chirality recognition based on adduct formation between a chiral metal chelate and optically active isomers. It was possible to differentiate clearly between the adduct formation of quinine and that of quinidine in the synergic extraction of cobalt and europium with 3-heptafluorobutyryl- d-camphor and cobalt with 3-trifluoroacetyl-d-camphor.     

Improvement of the hydrothermal stability of MCM-48 mesoporous molecular sieves

This is a review of our recent reports about improving the hydrothermal stability of MCM-48 mesoporous molecular sieves and the related works done by other groups. It presents the different effects of direct addition of various anions, including F^?, SO₄ ^2?, NO₃ ^? and Cl^?, on the improvement of the hydrothermal stability of MCM-48. The different effects of anions on the improvement of the hydrothermal stability and the critical factors influencing the formation of hydrothermally stable MCM-48 are also explained by careful analysis and discussion.