Electrochemical Measurements of Optogenetically Stimulated Quantal Amine Release from Single Nerve Cell Varicosities in Drosophila Larvae

The nerve terminals found in the body wall of Drosophila melanogaster larvae are readily accessible to experimental manipulation. We used the light‐activated ion channel, channelrhodopsin‐2, which is expressed by genetic manipulation in Type II varicosities to study octopamine release in Drosophila. We report the development of a method to measure neurotransmitter release from exocytosis events at individual varicosities in the Drosophila larval system by amperometry. A microelectrode was placed in a region of the muscle containing a varicosity and held at a potential sufficient to oxidize octopamine and the terminal stimulated by blue light. Optical stimulation of Type II boutons evokes exocytosis of octopamine, which is detected through oxidization at the electrode surface. We observe 22700±4200 molecules of octopamine released per vesicle. This system provides a genetically accessible platform to study the regulation of amine release at an intact synapse.     

A study of the charge propagation in nanoparticles of Fe2O3 core-cobalt hexacyanoferrate shell by chronoamperometry and electrochemical impedance spectroscopy

A composite electrode comprised of graphite, Nujol, and nanoparticles of Fe₂O₃ core–cobalt hexacyanoferrate shell was prepared and the charge transport processes in the bulk of this composite were studied. The electrode/solution interface was assumed as a binary electrolyte whose charge transport occurred between redox sites of the nanoparticles present in the composite and counter cations present in the solution. Using cyclic voltammetry, the diffusion of counter cation in the shell was investigated. Using chronoamperometry, an effective diffusion coefficient and its dependency on the applied potential was obtained. In the Nyquist diagrams, different time constants were appeared with relation to different physical and electrochemical processes. Percolation of electron in the shell of the nanoparticles appeared at very high frequencies and exhibited the feature of a diffusion process with a transmissive boundary condition at interface of core–shell structure/graphite particles. The diffusion coefficients of electron and counter cation and the standard rate constants of each individual electrochemical reaction were obtained.     

Coadjoint Orbits of Certain Motion Groups and Their Coherent States

Let ?_n, n ≥ 1, be the (2n+1)-dimensional Heisenberg group and let K be a closed connected subgroup of the unitary group U(n) acting on ?_n by automorphisms. Using the moment map, we provide in this paper a dequantization procedure for all generic admissible coadjoint orbits of the semidirect product G = K ? ?_n. In the opposite direction, we show that Gilmore-Perelomov's coherent states define “pure state quantizations” of such orbits.     

Prediction of the existence of the N2H- molecular anion

We predict the existence of the N(2)H(-) anion from first principle calculations. We present the three-dimensional potential energy surface and the bound states of the N(2)H(-)/D(-) van der Waals anion. The electronic calculations were performed using state-of-the-art ab initio methods and the nuclear motions were solved using a quantum close-coupling scattering theory. A T-shaped equilibrium structure was found, with a well depth of 349.1 cm(-1), where 18 bound states have been located for N(2)H(-) and 25 for N(2)D(-) for total angular momentum J = 0. We also present the absorption spectra of the N(2)H(-) complex. This anion could be formed after low energy collisions between N(2) and H(-) through radiative association. The importance of this prediction in astrophysics and the possible use of N(2)H(-) as a tracer of N(2) and H(-) in the interstellar medium is discussed.     

Flavones and rosmarinic acid from Salvia limbata

The genus Salvia (Lamiaceae) contains more than 50 shrub species in Iran, and Salvia limbata C.A. Meyer grows widely in the north and central parts of the country. Six flavones and rosmarinic acid were isolated from the ethyl acetate and methanol extracts of the flowered aerial parts of S. limbata collected from Semnan province. The separation process was carried out using several chromatographic methods. Structural elucidation was based on NMR data, in comparison with those reported in the literature. The isolated compounds were identified as ladanein (1), salvigenin (2), luteolin 7-methyl ether (3), cirsiliol (4), eupatorin (5), luteolin 7-O-glucoside (6) and rosmarinic acid (7). Some of these flavonoids have been reported to show antibacterial and cytotoxic activities.     

A Comparative Study of Anti-Candida Activity and Phenolic Contents of the Calluses from Lythrum salicaria L. in Different Treatments

In the study, anti-Candida activity and phenol contents of Lythrum salicaria L. calli and wild species have been evaluated. The seeds of L. salicaria (Lythraceae), collected from Lahidjan City in the north of Iran, were cultured in Murashige and Skoog medium (MSM) with a supplement, gibberellin, to germinate. Callus inductions were performed from segments of seedling on MSM containing different concentrations of plant growth regulators, 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP). The activity of calluses extracts, wild plant, gallic acid, and 3,3′,4′-tri-O-methylellagic acid-4-O-β-d-glucopyranoside (TMEG) as the main phenolic compounds against Candida albicans was assessed using cup plate diffusion method. The total phenols contents of calli and wild plant extracts were analyzed using Folin–Ciocalteu reagent. The callus formation in MSM supplemented with various concentrations of 2,4-D and BAP were 0–100 %. Anti-Candida activity of callus extract which obtained from MSM supplemented with 2,4-D and BAP (1 mg?dm^?3) was similar to the wild plant extract. Minimum inhibitory concentration values of gallic acid and TMEG were obtained as 0.312 and 2.5 mg?cm^?3, respectively. Gallic acid equivalent values in all treatments were from 0 to 288 μg GAE mg^?1. Phenolic contents of plant aerial parts (331?±?3.7 μg GAE mg^?1) and the callus, which developed in MSM including 1 mg?dm^?3 of both 2,4-D and BAP, showed the same phenolic value and exhibited anti-Candida extract activity.     

用于大肠杆菌消毒的负载型和悬浮型TiO_2催化剂的动力学和催化效率（英文）

TiO2‐mediated photocatalysis is widely used in a variety of applications and products in the envi‐ronmental and energy fields, including photoelectrochemical conversion, self‐cleaning surfaces, and especially water purification systems. The dimensionality of the structure of a TiO2 material can affect its properties, functions, and more specifically, its photocatalytic performance. In this work, the photocatalytic inactivation of Gram‐negative Escherichia coli using three photocatalysts, differ‐ing in their structure and other characteristics, was studied in a batch reactor under UVA light. The aim was to establish the disinfection efficiency of solid TiO2 compared with that of suspended cata‐lysts, widely considered as reference cases for photocatalytic water disinfection. The bacterial inac‐tivation profiles obtained showed that: (1) the photoinactivation was exclusively related to the quantity of photons retained per unit of treated volume, irrespective of the characteristics of the photocatalyst and the emitted light flux densities;(2) across the whole UV light range studied, each of the photocatalytic solids was able to achieve more than 2 log bacterial inactivation with less than 2 h UV irradiation;(3) none of the used catalysts achieved a total bacterial disinfection during the treatment time. For each of the catalysts the quantum yield has been assessed in terms of disinfec‐tion efficiency, the 2D material showed almost the same performance as those of suspended cata‐lysts. This catalyst is promising for supported photocatalysis applications.     

Electrochemical oxidation and determination of ceftriaxone on a glassy carbon and carbon-nanotube-modified glassy carbon electrodes

The electrochemical behavior of ceftriaxone was investigated on a carbon-nanotube-modified glassy carbon (GC-CNT) electrode in a phosphate buffer solution, pH = 7.40, and the results were compared with those obtained using the unmodified one [glassy carbon (GC) electrode]. During oxidation of ceftriaxone, an irreversible anodic peak appeared, using both modified and unmodified electrodes. Cyclic voltammetric studies indicated that the oxidation process is irreversible and diffusion-controlled. The number of electrons exchanged in the electrooxidation process was obtained, and the data indicated that ceftriaxone is oxidized via a one-electron step. The results revealed that carbon nanotube promotes the rate of oxidation by increasing the peak current. In addition, ceftriaxone was oxidized at lower potentials, which thermodynamically is more favorable. These results were confirmed by impedance measurements. The electron-transfer coefficients and heterogeneous electron-transfer rate constants for ceftriaxone were reported using both the GC and GC-CNT electrodes. Furthermore, the diffusion coefficient of ceftriaxone was found to be 2.74 × 10⁻⁶ cm² s⁻¹. Binding of ceftriaxone to human serum albumin forms a kind of electroreactive species. The percentage of interaction of ceftriaxone with protein was also addressed. A sensitive, simple, and time-saving differential-pulse voltammetric procedure was developed for the analysis of ceftriaxone, using the GC-CNT electrode. Ceftriaxone can be determined with a detection limit of 4.03 × 10⁻⁶ M with the proposed method.     

A combined experimental and theoretical study on p‐sulfonatocalix[4]arene encapsulated 7‐methoxycoumarin

Host‐guest interactions are essential in chemistry, biology, medicine and environmental science. In this combined experimental and theoretical contribution, the encapsulation of 7‐methoxycoumarin (herniarin, 7MC) with p‐sulfonatocalix[4]arene (p‐SC4) is studied using absorption and fluorescence spectroscopy, cyclic voltammetry and computational approaches. The 1:1 stoichiometry is confirmed using Job's plot. Our results show that the keto group of 7MC is the main source for electrochemical conversion of this complex. The excited state 7MC radiative decay is studied using time‐correlated single photon counting technique. The computed UV‐Vis absorption spectra for this complex at gas phase and solvent are online with the experimental spectra. Moreover, we determined the binding energy and the binding constant of the 7MC‐p‐SC4 complex. Density functional theory computations revealed that stabilization of the complex formed by p‐SC4 and 7MC is due to weak noncovalent and dispersive types of interactions. A comparison with encapsulation of amino acids by p‐SC4 is also conducted. Finally, we show that the flexibility of p‐SC4 and the weak nature of its interaction with 7MC are on the origin of the reversibility of encapsulation, which is mandatory for applications such as drug delivery.     

Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN

The phytochemical investigation of Scilla persica HAUSSKN bulbs led to the isolation of a novel homoisoflavonoid that named Scillapersicene (1) and identified as 3-(3′,4′-dihydroxybenzylidene)-8-hydroxy-5,7-dimethoxychroman-4-one along with five known homoisoflavonoids 2–6, whose structures were elucidated using HRFAB-MS, 1D and 2D NMR spectroscopic data. The known compounds were identified as 3-(3′,4′-dihydroxybenzyl)-5,8-dihydroxy-7-methoxychroman-4-one (2), 3,9-dihydro-autumnalin (3), autumnalin (4), 3-(3′,4′-dihydroxybenzylidene)-5,8-dihydroxy-7-methoxychroman-4-one (5) and scillapersicone (6). All compounds obtained, expect 2 and 4, showed strong cytotoxic activity against AGS cell line. The toxicity on AGS cell line was measured by 1, 3, 5 and 6 with IC₅₀ values of 8.4, 30.5, 10.7 and 24.2 μM, respectively. In addition, the physico-chemical properties of these natural compounds were optimised using density functional method (B3LYP) with standard 6-311+G* basis set. These natural products have low-energy gaps between the first ionisation potentials and highest occupied molecular orbital. In conclusion, the low-energy gap could cause reason for cytotoxic activity of homoisoflavonoids.