Synthesis,stability, and spectroscopic and electronic properties of three benzocyclohepta[alpha]azulenylium ions

Novel pi-systems, three benzocyclohepta[alpha]azulenylium ions, 7a-c, are synthesized, and their stability and properties have been characterized in terms of the position of the benzo-annulation and compared with those of the parent cyclohepta[alpha]azulenylium ion 4. Benzocyclohepta[6,7-alpha]azulenylium ion (7a) (p K R+ = 7.3, E red = -0.567 V vs Ag/Ag+) and benzocyclohepta[6,5-alpha]azulenylium ion (7b) (p K R+ = 5.1, E red = -0.482 V vs Ag/Ag+), which are annulated with benzene on the position having a high bond order of 4, are not appreciably destabilized compared with cyclohepta[alpha]azulenylium ion (4) (p K R+ = 7.3, E red = -0.458 V vs Ag/Ag+). On the other hand, benzocyclohepta[7,6-alpha]azulenylium ion (7c) (p K R+ = 1.6, Ered = -0.197 V vs Ag/Ag+) is considerably destabilized, probably due to enhanced contribution of the quinoid structure of the benzene ring, which is annulated on the position having a low bond order of the cyclohepta[alpha]azulenylium ion moiety. Furthermore, the cations 7a and 7b are more stable than 12,13-dihydrobenzocyclohepta[7,6-alpha]azulenylium ion (25) (p K R+ = 4.8, E red = -0.513 V vs Ag/Ag+), which is a dihydrogenated compound of 7a, while 7c is less stable than 25. These features are reflected in the considerable red shift of the longest absorption maximum of the electronic spectrum of 7c, as compared with those of 4, 7a, and 7b, and in the chemical shifts of the protons and their coupling constants of the (1)H NMR spectra. Furthermore, the (1)H NMR spectra and electronic spectra of 5H-benzocyclohepta[6,7-alpha]azulen-5-one (8a) and 7H-benzocyclohepta[6,5-alpha]azulen-7-one (8b) in acidic media have also been studied to clarify the spectral characteristics similar to those of 7a and 7b.     

Reverse permeation of sodium ions driven by pH difference across a liquid membrane: time dependencies of membrane resistance and membrane potential in a reverse permeation system

The diffusional flux of sodium ions across a liquid membrane was observed as a reverse permeation phenomenon: sodium ions were transported across the membrane against their own concentration difference. A supported liquid membrane having stearic acid as an ionic carrier was used. The internal aqueous phase contained NaCl and HCl and the external aqueous phase contained NaOH of the same initial concentration as NaCl in the internal aqueous phase. The reverse permeation occurred with a long time delay. During the delay, sodium ions flowed from the acidic to alkaline solution. The diffusion coefficient of sodium ion estimated from the flux equation taking into account the Donnan equilibrium at the interface was found to be much greater than that in the membrane solvent, 1-octanol. In the same membrane system as for the flux measurement, the membrane conductance and the membrane potential were measured as a function of time. The time dependence of the membrane potential in the presteady state showed a biphasic behavior. The initial rapid phase could be attributed to the change in the phase boundary potential and the subsequent slow step to the change in the diffusion potential within the membrane. Before the steady membrane potential had been reached, the reverse permeation of sodium ions against their own concentration difference was not observed. During the slow relaxation process of the membrane potential, the membrane resistance decreased to approach the steady state. Moreover, the oscillation of membrane potential abruptly started at a time in the slow step of the potential change and continued during the steady state. It was suggested that, at the presteady state, the increase in the amount of water in the membrane would drive a drastic change in the state of the liquid membrane in the filter pore, e.g. an inverted micellar structure making.     

Simultaneous determination of bromide and iodide ions by capillary isotachophoresis using quaternary ammonium salts

Bromide and iodide ions were determined simultaneously by capillary isotachophoresis using an aqueous electrolyte system; the separation principle was based on the ion-pairing equilibria between tetradecyldimethylbenzylammonium ion and these anions in the leading electrolyte. The interaction between iodide ion and tetradecyldimethylbenzylammonium ion was stronger than that for bromide ion. Thus complete separation of bromide and iodide ions could be obtained by using a leading electrolyte containing 1.5 mM tetradecyldimethylbenzylammonium ion. The pH of the leading electrolyte was adjusted to 5.0. The relative standard deviations of the zone length for bromide and iodide ions were 1.1 and 1.2%, respectively, when mixture of 3.0 mM of these ions was analysed. A 150-μl volume could be injected for the simultaneous determination of low concentrations of bromide and iodide ions.     

THE 'OPSIN SHIFT' IN BACTERIORHODOPSIN: STUDIES WITH ARTIFICIAL BACTERIORHODOPSINS

Abstract— The difference (in cm⁻¹) in absorption maxima between the protonated Schiff base of retinals and the pigment derived therefrom has been defined as the opsin shift. It represents the influence of the opsin binding site on the chromophore. The analysis of the opsin shifts of a series of dihydrobacteriorhodopsins has led to the external point-charge model, which in addition to a counter anion near the Schiff base ammonium, carries another negative charge in the vicinity of the β-ionone ring. This is in striking contrast to the external point-charge model proposed earlier for the bovine visual pigment. The absorption maxima of rhodopsins formed from bromo- and phenyl retinals support the two models. A retinal carrying a photoaffinity label has yielded a nonbleachable bacteriorhodopsin.     

Extraction equilibria for the 4-(2-Pyridylazo)-Resorcinol-Nickel(II)-Quaternary-Ammonium salt system

The extraction equilibria of nickel(II)-PAR complexes with tetradecyldimethylbenzylammonium chloride(Q⁺Cl^?) are investigated. Two kinds of nickel complex are extracted by chloroform: Ni(HR)₂,nQ⁺Cl^?₍₀₎(?⁵⁰⁰ = 3.73·10⁴l mol^?1cm^?1) at about pH 5 and 2Q⁺ NiR^2-_2(o)(?⁵⁰⁰ = 8.08·10⁴ l mol^?1 cm^?1) at above pH 8.5. The extraction constant for 2Q⁺ NiR^2-_2(o) was evaluated as [2Q⁺ NiR^2-₂]₀/[NiR^2-₂] [Q⁺]² = 10^11.16 at μ = 0.1 (Na₂SO₄. Synergic extraction studies of the Ni(HR)₂ species under slightly acidic conditions show that the species is Ni(HR)₂(H₂O)₂in auqeous solution and is extracted into chloroform as the adduct Ni(HR)₂(TBP)₂ (?⁵³⁵ = 3.57·10⁴ l mol^?1 cm^?1. Based on the extraction behavior of these complexes, the structures of the Ni²⁺—PAR complexes are discussed.     

Ionic conduction of the perovskite-type halides

The ionic conduction in the perovskite-type halides, CsPbCl₃, CsPbCl₃ and KMnCl₃, was studied. Measurements were made of ac conductivity at temperatures from 150°C to the melting point, and of ionic transport number using the Tubandt, EMF and ion-blocking methods. The effects of impurity doping on the ionic conductivity of CsPbCl₃ were also studied using the samples of composition, CsPb_0.99M_0.01Cl_2.99 (M = Li, Na, K, Ag). It was concluded that these materials are halide-ion condcutors. The ionic conductivities of CsPbCl₃ and CsPbBr₃ are close to those of the well known halide-ion conductors, PbCl₂ and PbBr₂. The ionic transport numbers were found to be > 0.9 for CsPbCl₃ and CsPbBr₃, and about 0.99 for KMnCl₃. The conduction was considered to be caused by the migration of halide-ion vacancies V_X (X = Cl, Br). The activation energies for the migration of V_X were 0.29 eV for CsPbCl₃, 0.25 eV for CsPbBr₃ and 0.39 eV for KMnCl₃. The vacancy diffusion coefficients of these materials were found to be verylarge. However, the impurity doping did not increase the ionic conductivity markedly because of small dopant solubility.     

ESR study of the xenon-photosensitized decomposition of gaseous hydrogen

The gas-phase ESR technique has been used to study the xenon-photosensitization of hydrogen. The ESR spectrum of atomic hydrogen was observed when the mixtures of xenon and hydrogen were irradiated by the xenon resonance line (147 nm). The results show that photosensitized decomposition of hydrogen takes place due to the chemical quenching of the excited xenon by hydrogen molecules.     

Isolation of heptadepsin, a novel bacterial cyclic depsipeptide that inhibits lipopolysaccharide activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.     

Power-free poly(dimethylsiloxane) microfluidic devices for gold nanoparticle-based DNA analysis

An extremely simple, power-free pumping method for poly(dimethylsiloxane)(PDMS) microfluidic devices is presented. By exploiting the high gas solubility of PDMS, the energy for the pumping is pre-stored in the degassed bulk PDMS, therefore no additional structures other than channels and reservoirs are required. In a Y-shaped microchannel with cross section of 100 microm width x 25 microm height, this method has provided flow rate of 0.5-2 nL s(-1), corresponding to linear velocity of 0.2-0.8 mm s(-1), with good reproducibility. As an application of the power-free pumping, gold nanoparticle-based DNA analysis, which does not rely on the cross-linking mechanism between nanoparticles, has been implemented in a microchannel with three inlets. Target 15mer DNA has been easily and unambiguously discriminated from its single-base substituted mutant. Instead of colorimetric detection in a conventional microtube, an alternative detection technique suitable for microdevices has been discovered-observation of deposition on the PDMS surfaces. The channel layout enabled two simultaneous DNA analyses at the two interfaces between the three laminar streams.     

Chlorovulones,new halogenated marine prostanoids with an antitumor activity from the stolonifer clavularia viridis Quoy and Gaimard

New halogenated marine prostanoids, chlorovulone I, II and III were isolated from the stolonifer $\text{Clavularia}$$\text{viridis}$ Quoy and Gaimard. The structure elucidation and the antitumor activity of chlorovulones were described.