Liposome-based measurement of light-driven chloride transport kinetics of halorhodopsin.

We report a simple and direct fluorimetric vesicle-based method for measuring the transport rate of the light-driven ions pumps as specifically applied to the chloride pump, halorhodopsin, from Natronomonas pharaonis (pHR). Previous measurements were cell-based and methods to determine average single channel permeability challenging. We used a water-in-oil emulsion method for directional pHR reconstitution into two different types of vesicles: lipid vesicles and asymmetric lipid-block copolymer vesicles. We then used stopped-flow experiments combined with fluorescence correlation spectroscopy to determine per protein Cl- transport rates. We obtained a Cl- transport rate of 442 (±17.7) Cl-/protein/s in egg phosphatidyl choline (PC) lipid vesicles and 413 (±26) Cl-/protein/s in hybrid block copolymer/lipid (BCP/PC) vesicles with polybutadine-polyethylene oxide (PB12PEO8) on the outer leaflet and PC in the inner leaflet at a photon flux of 1450 photons/protein/s. Normalizing to a per photon basis, this corresponds to 0.30 (±0.07) Cl-/photon and 0.28 (±0.04) Cl-/photon for pure PC and BCP/PC hybrid vesicles respectively, both of which are in agreement with recently reported turnover of ~500 Cl-/protein/s from flash photolysis experiments and with voltage-clamp measurements of 0.35 (±0.16) Cl-/photon in pHR-expressing oocytes as well as with a pHR quantum efficiency of ~30%.

Chloride ion-driven transformation from Ag3PO4 to AgCl on the hydroxyapatite support and its dual antibacterial effect against Escherichia coli under visible light irradiation.

Visible light-driven photocatalytic inactivation of Escherichia coli was performed using hydroxyapatite-supported Ag3PO4 nanocomposites (Ag3PO4/HA). The antibacterial performance was evaluated by the methods of zone of inhibition plates and minimum inhibitory concentration test. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to investigate the instability and transformation of the nanocomposite by comparing the crystalline, phase, and the morphology before and after exposure to Luria-Bertani culture medium under visible light irradiation. Ag3PO4 nanoparticles on the support were found to be shortly transformed into AgCl due to high chloride concentration of Luria-Bertani culture medium. The AgCl/HA nanocomposite showed both excellent intrinsic antibacterial performance contributed by the released silver ions and visible light-induced photocatalytic disinfection toward E. coli cells. This dual antibacterial function mechanism was validated by trapping the hydroxyl free radical and detecting the silver ions during the photocatalytic antibacterial process. The morphological change of E. coli cells in different reaction intervals was obtained by scanning electron microscopy (SEM) to complementally verify photocatalytic inactivation of E. coli. This work suggests that an essential comparison study is required for the antibacterial materials before and after the photocatalytic inactivation of bacterial cells using Ag3PO4 nanoparticles or Ag3PO4-related nanocomposites in mediums containing high-concentration chloride ions.

Aniline chlorination by in situ formed Ag-Cl complexes under simulated solar light irradiation.

Ag speciation in a chloride medium was dependent upon the Cl/Ag ratio after releasing into surface water. In this study, the photoreaction of in situ formed Ag-Cl species and their effects on aniline photochlorination were systematically investigated. Our results suggested that formation of chloroaniline was strongly relevant to the Cl/Ag ratio and could be interpreted using the thermodynamically expected speciation of Ag in the presence of Cl-. AgCl was the main species responsible for the photochlorination of aniline. Both photoinduced hole and •OH drove the oxidation of Cl- to radical •Cl, which promoted the chlorination of aniline. Ag0 formation was observed from the surface plasmon resonance absorption during AgCl photoreaction. This study revealed that Ag+ released into Cl--containing water may result in the formation of chlorinated intermediates of organic compounds under solar light irradiation.

Reduction of aryl halides by consecutive visible light-induced electron transfer processes.

Biological photosynthesis uses the energy of several visible light photons for the challenging oxidation of water, whereas chemical photocatalysis typically involves only single-photon excitation. Perylene bisimide is reduced by visible light photoinduced electron transfer (PET) to its stable and colored radical anion. We report here that subsequent excitation of the radical anion accumulates sufficient energy for the reduction of stable aryl chlorides giving aryl radicals, which were trapped by hydrogen atom donors or used in carbon-carbon bond formation. This consecutive PET (conPET) overcomes the current energetic limitation of visible light photoredox catalysis and allows the photocatalytic conversion of less reactive chemical bonds in organic synthesis.

82Sr purification procedure using Chelex-100 resin.

(82)Rb is a positron-emitting radionuclide widely used in nuclear cardiology. One great advantage is its availability through a generator loaded with (82)Sr. (82)Sr can be produced in a high energy cyclotron by irradiating rubidium chloride target with proton beam. In this paper, we present an extensive study (elution profiles, effect of the elution flow rate) on the use of Chelex-100 resin and ammonia buffer. No significant effect of flow rate was evidenced between 1 and 10mL/min leading us to propose a purification process which can be easily automated.

Cl2 deposition on soil matrices.

Deposition of chlorine gas, Cl(2), on synthetic soil sample matrices was examined in a small chamber to ascertain its potential significance as a chemical sink during large-scale releases. The effects of organic matter, clay and sand mass fractions of the soil matrix, soil packing, and exposure to ultraviolet (UV) light on the observed Cl(2) deposition were examined. Organic matter content was found to be the dominant soil variable investigated that affected Cl(2) deposition; all other variables exhibited no measurable effect. Analytical results from the top 8.5mm of soil columns exposed to Cl(2) were fit to a simple kinetic model with six adjustable parameters. The kinetic model included two reactive bins to account for fast- and slow-reacting material in the soil matrices. The resulting empirical equation agreed with the data to within a factor of two and accurately predicted results from soil mixes not used to optimize the adjustable parameters. Total Cl(2) deposition, assuming a penetration depth of 8.5mm, was calculated to be as high as 160 metric tons per square kilometer for soil with an organic content of 10%, and inferred deposition velocities were as high as 0.5 cm/s for organically rich soil.

Ultrasound-promoted synthesis of novel bipodal and tripodalpiperidin-4-ones and silica chloride mediated conversion to its piperidin-4-ols: synthesis and structural confinements.

The ultrasound-promoted synthesis of novel bipodal and tripodalpiperidin-4-ones was carried out by the reaction of 4-piperidone hydrochloride monohydrate with different alkylating and acylating agents. It was preferably reduced to respective piperidin-4-ols by ultrasonic irradiation using silica chloride, which maintains higher yields by acting as an effective supporting polymer. The sterically hindered phthaloyl derivative of piperidin-4-one was synthesized by ultrasonic irradiation which was difficult by conventional methods.

Photooxidation of chloride by oxide minerals: implications for perchlorate on Mars.

We show that highly oxidizing valence band holes, produced by ultraviolet (UV) illumination of naturally occurring semiconducting minerals, are capable of oxidizing chloride ion to perchlorate in aqueous solutions at higher rates than other known natural perchlorate production processes. Our results support an alternative to atmospheric reactions leading to the formation of high concentrations of perchlorate on Mars.

An efficient sonochemical oxidation of benzyl alcohols into benzaldehydes by FeCl3/HNO3 in acetone.

Sonochemical oxidation of benzyl alcohols into corresponding aldehydes by FeCl(3)/HNO(3) in acetone at room temperature has been reported. All substrates give good yield of the products within 10-25 min. The reaction of selected substrates were also studied under reflux and at the room temperature. Further, various Lewis acids were used to evaluate their catalytic efficacy.

Degradation of a mixture of pollutants in water using the UV/H2O2 process.

The degradation reaction of a simple mixture of pollutants (dichloroacetic acid + formic acid) employing H2O2 and UVC radiation (253.7 nm) has been studied in a well-mixed reactor which operates inside a recycling system. The aim of this work is to develop a systematic methodology for treating degradation of mixtures of pollutants, starting from a rather manageable system to more complex aggregates. In this contribution, the effects of different variables such as hydrogen peroxide/pollutant mixture initial concentration ratio, pH and incident radiation at the reactor wall were studied. The results show that the best degrading conditions are: pH = 3.5 and hydrogen peroxide concentrations from 3.9 to 11.8 mM (134-400 mg/L), for initial concentrations of 1.10 and 0.39 mM for formic acid and dichoroacetic acid respectively (50 mg/L for both pollutants). The influence of the incident radiation at the reactor wall on the degradation rates of the mixture is significant. In addition to this, it has been shown that in the employed aqueous solution no stable reaction intermediates are formed. On this basis, a complete reaction scheme for the mixture is proposed that is suitable for a reaction kinetics mathematical modeling of the mixture and further studies of increasing complexity.

Studies on destruction of silicon tetrachloride using microwave plasma jet.

A new method for destroying silicon tetrachloride has been proposed, which is based on a microwave plasma jet that operates at atmospheric pressure using hydrogen as work gas. The influence of input power (P) and silicon tetrachloride concentration (phi) on the percent destruction and removal of SiCl(4) was investigated. And the reclaimed solid byproducts were characterized by SEM, EDX and XRD. Species in the plasma, which were identified by atomic emission spectroscopy were found to include no halogen. Results indicate that the destruction efficiency of silicon tetrachloride can reach 96% when P=800 W and phi=1.0%, and the main solid byproduct was Si. The silicon deposited on the molybdenum substrate of the plasma reactor was yellow and typical nano-sized particles with grain size of 54 nm.

Ultrasound promoted ZrCl(4) catalyzed rapid synthesis of substituted 1,2,3,4-tetrahydropyrimidine-2-ones in solvent or dry media.

Sonication of aromatic aldehydes, urea and ethyl acetoacetate in presence of solvent (ethyl alcohol) or solvent-less dry media (bentonite clay) supported-zirconium (IV) chloride (ZrCl(4)) as catalyst at 35 kHz gives 6-methyl-4-substitutedphenyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl esters proficiently in high yields.

EPR characteristics of chloride-depleted photosystem II membranes in the presence of other anions.

Chloride is an essential cofactor for the oxidation of water to oxygen. Anion substitution (Br(-), I(-), NO(2)(-), F(-)) in Cl(-)-depleted PS II membranes brings out significant changes in the EPR signals arising from the S(2) state and from the iron-quinone complex of PS II. On the basis of the changes observed in the S(2) state multiline signal and the Q(A)Fe(3+) EPR signal in Cl(-)-depleted PS II membranes after substituting with various anions, we report a possible binding site of anions such as chloride and bromide at the PS II donor side as well as at the acceptor side.

Aggregation of photolytic gold nanoparticles at the surface of chitosan films.

Formation and aggregation of photolytic gold nanoparticles at the surface of chitosan (CTO) films have been investigated. When thin films of chloroauric acid salt of CTO were irradiated with UV light in wet air at room temperature for 10 min, gold nanoparticles of approximately 10 nm size are formed at the film surface. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize gold nanoparticles at the film surface. The shift of Au(4f) peak to the higher energy side and broadening of full width at half-maximum in the XPS spectrum are the direct evidence of the existence of gold atoms and small clusters in the early stage of photolysis. According to FE-SEM observation, growth in the particle diameter and aggregation of nanoparticles were observed after prolonged irradiation, and, finally, the film surface was densely covered with gold particles of 20-100-nm size. Gold atoms and clusters could move in the film and precipitate to the irradiated surface. Chemical composition analysis further suggests that gold particles at the surface are covered with an ultrathin CTO layer, which is partly oxidized by oxygen and chlorinated by chlorine during photochemical reactions.

Thermoluminescence of photostimulable materials after X irradiation below room temperature.

Thermoluminescence glow peaks in the temperature range 100 to 400 K are investigated for BaFX (X = Cl, Br) crystals after X irradiation at 100 K. A prominent glow peak of BaFCl around 210 K is found to be composed of a few recombination roots, that is, the peak corresponds to the recombination of hole trapped centres such as an O- centre and a dissociated Cl2- centre with the F (F-) centre and the O2--F(Cl-) pair defect. Another small glow peak around 270 K is likely to occur from thermal dissociation of the O2- -F(Cl-) pair defect. The main glow peak of BaFBr:O2- at 170 K may be attributed to a recombination of an O- centre with the F(Br-) centre.

An EPR study of the transfer and trapping of holes produced by radiation in guanine(thioguanine) hydrochloride single crystals.

Single crystals of guanine hydrochloride monohydrate, guanine hydrochloride dihydrate and anhydrous guanine dihydrochloride, doped with thioguanine, were irradiated with X and gamma rays. In all three systems the dominant radicals were associated with thioguanine. In the former two systems the stabilized species is the thiyl radical, formed by initial loss of an electron at some of the guanines in the crystal lattice, followed by hole migration to thioguanine and subsequent deprotonation of the radical formed. In the anhydrous guanine(thioguanine) dihydrochloride, that process is followed by acquisition of a chlorine ion. In the guanine hydrochloride monohydrate and guanine hydrochloride dihydrate lattices, systems of interacting closely spaced stacked bases and strings of chloride ions might support the migration of electrons and/or holes. In anhydrous guanine dihydrochloride, neither the bases nor the Cl- ions alone are capable of providing the means for the long-range electron, energy and spin transfer. It is the interchangeable sequence of the charged bases and the Cl- ions that makes the supporting strings or networks. The ultimate chlorination of the thioguanine-centered electron-loss radicals depends mainly on the availability of the Cl- ions and the space for their accommodation in the vicinity of the sulfur atom.

Radiation-induced generation of chlorine derivatives in N2O-saturated phosphate buffered saline: toxic effects on Escherichia coli cells.

The radiolysis of aqueous chloride solutions has been investigated using pulse and steady-state methods. We have found a correlation between the yields of Cl2- and HOCl formed in pulse-irradiated N2O-saturated solutions. The yields increased with the increasing concentrations of Cl- and phosphate. Phosphate enhanced the yield of Cl2- in neutral solutions because of a proton transfer from H2PO4- to HOCl- with a rate constant of (2.6 +/- 0.5) x 10(8) M-1s-1. HOCl could not be detected in pulse-irradiated He or air-saturated, phosphate-buffered saline (PBS) solutions or in gamma-irradiated N2O, He, or air-saturated PBS solutions. The results are discussed in light of previously suggested mechanisms for the formation and decay of Cl2-. Pulse-irradiated N2O-saturated PBS solutions have a lethal effect on Escherichia coli cells, which is proportional to the amount of HOCl in the solutions. Gamma-irradiation of cells in N2O-saturated PBS solution also raises the radiosensitivity of the cells, although HOCl does not accumulate in this system. The effects of the radiation-induced toxic products on E. coli cells are similar to the effects of NaOCl. The cell membrane is probably the site of physiological injury induced by the radiation products.

Horseradish peroxidase. XXXIV. Oxidation of compound II to I by periodate and inorganic anion radicals.

The one-electron oxidation of horseradish peroxidase compound II to compound I by sodium periodate was observed. The bimolecular rate constant for the NaIO4--compound II interaction is equal to 9.5 +/- 1 x 10(-3) M-1s-1 at room temperature. Irradiation, using ultraviolet light, of the solution containing compound II and persulfate in the presence of bicarbonate, chloride, or bromide, leads ot the fast accumulation of compound I due to the oxidative action of SO4, CO3, Cl2, and Br2 anion radicals, which are products of the photolysis.