Smart electrochemical sensor for some neurotransmitters using imprinted sol-gel films

A hybrid sol-gel material formed by acid hydrolysis of a mixture of tetraethylorthosilicate (TEOS) and phenyltriethylorthosilicate (PTEOS) as functional monomers was imprinted by tyramine and dopamine as template molecules for the purpose of molecular recognition. Imprinted materials were spin coated as thin films on the surface of glassy carbon electrodes and then were characterized using cyclic voltammetry (CV). After extraction of the encapsulated molecules, imprinted films were tested in solutions of their templates and other molecules. Rebinding experiments were followed by electrochemical characterization using square wave voltammetry (SWV). Imprinted films showed higher affinities toward their template molecules compared to other structurally similar molecules especially for tyramine imprinted film. With the exception of tyramine and norepinephrine, the interference level did not exceed 5% for all compounds studied for dopamine-imprinted films. Tyramine-imprinted films however showed high affinity to tyramine with dopamine 40% interference. Some factors related to the rebinding ability process like pH of solution, concentration of template were studied. The sensing surface lifetime extended to 2 weeks with decay in response signal that ranged from 22%, 40% to 60% for dopamine, tyramine and norepinephrine, respectively. The standard deviation from the mean of measurements for the repeated experiments is 7.4%. Electrochemical impedance spectroscopy (EIS) measurements confirmed the results obtained by electrochemical measurements. Morphological characteristics of the imprinted thin films and their thickness were investigated using scanning electron microscope (SEM).     

Mechanism for nuclear excitation during positron annihilation using Coulomb wave functions

We have calculated cross sections for the process of nuclear excitation during positron annihilation on any bound electron. We used Coulomb wave functions for the electron and positron.     

Self-Organization of Lipid-Porphyrin Conjugates at the Air/Water Interface

Lipid-porphyrin conjugates are versatile compounds which can self-assemble into liposome-like structures with multifunctional properties. Most of the conjugates that have been described so far, consisted in grafting pyropheophorbide-a (Pyro-a) or other porphyrin derivatives through the esterification of the hydroxyl group in the sn-2 position of a lysophosphatidylcholine. However, despite the versatility of these conjugates, less is known about the impact of the lipid backbone structure on their 2D phase behavior at the air/water interface and more precisely on their fine structures normal to the interface as well as on their in-plane organization. Herein, we synthesized a new lipid-porphyrin conjugate (PyroLSM) based on the amide coupling of Pyro-a to a lysosphingomyelin backbone (LSM) and we compared its interfacial behavior to that of Pyro-a and Pyro-a conjugated lysophosphatidylcholine (PyroLPC) using Langmuir balance combined to a variety of other physical techniques. Our results provided evidence on the significant impact of the lipid backbone on the lateral packing of the conjugates as well as on the shape and size of the formed domains. Compared to Pyro-a and PyroLPC monolayers, PyroLSM exhibited the highest lateral packing which highlights the role of the lipid backbone in controlling their 2D organization which in turn may impact the photophysical properties of their assemblies.     

Charge separation and surface reconstruction: a Mn2+ doping study

Hydrothermal synthesis of Mn doped anatase (TiO2) nanoparticles using scrolled nanotubes of TiO2 and MnCl2 as the starting materials is described. Incorporation of Mn2+ ions on the substitutional sites was confirmed using X-ray absorption fine structure (FT-XAFS) while the oxidation state Mn(II) and coordination environment were determined using both electron paramagnetic resonance (EPR) and X-ray absorption near edge spectroscopy (XANES). Two different hyperfine couplings of 96 and 86 G were found using high-field (130 GHz) EPR reporting that Mn atoms occupy two distinct sites: one undercoordinated (reconstructed surface) and the other octahedral crystalline geometry (nanoparticle core), respectively. It was found that Mn atoms that occupy surface layers are weakly bound to the anatase lattice and can be easily leached using simple dialysis, while those incorporated in the nanoparticle core are bound more strongly and cannot be removed by dialysis. Light excitation EPR reveals that Mn ions incorporated in the surface layers participate in the charge separation, while those trapped deeply in the nanoparticle core do not show any photoactivity. Doping of the core of nanoparticles with Mn2+ ions, on the other hand, enables synthesis of optically transparent films having superparamagnetic behavior at room temperatures with a saturation magnetic moment of 1.23 microB per Mn atom.     

Functionalized Tricyclic Cytosine Analogues Provide Nucleoside Fluorophores with Improved Photophysical Properties and a Range of Solvent Sensitivities

Tricyclic cytosines (tC and tC^O frameworks) have emerged as a unique class of fluorescent nucleobase analogues that minimally perturb the structure of B‐form DNA and that are not quenched in duplex nucleic acids. Systematic derivatization of these frameworks is a likely approach to improve on and diversify photophysical properties, but has not so far been examined. Synthetic methods were refined to improve on tolerance for electron‐donating and electron‐withdrawing groups, resulting in a series of eight new, fluorescent cytidine analogues. Photophysical studies show that substitution of the framework results in a pattern of effects largely consistent across tC and tC^O and provides nucleoside fluorophores that are brighter than either parent. Moreover, a range of solvent sensitivities is observed, offering promise that this family of probes can be extended to new applications that require reporting on the local environment.     

Addition of Nitromethane to a Disilene and a Digermene: Comparison to Surface Reactivity and the Facile Formation of 1,3,2‐Dioxazolidines

The addition of nitromethane to tetramesityldisilene and tetramesityldigermene leads to the formation of the novel 1,3,2,4,5‐dioxazadisil‐ and digermolidine ring systems, respectively. The 1,3,2,4,5‐dioxazadisilolidine isomerizes to the 1,4,2,3,5‐dioxazadisilolidine ring system, whereas the 1,3,2,4,5‐dioxazadigermolidine undergoes ring opening to the isomeric oxime. The preferential formation of the 1,3,2,4,5‐dioxazadisilolidine, and its rearrangement to a 1,4,2,3,5‐dioxazadisilolidine, provides support for the suggested reaction pathway between nitromethane and the Si(100) 2×1 reconstructed surface.     

Natural Phenolic Acid,Product of the Honey Bee,for the Control of Oxidative Stress,Peritoneal Angiogenesis,and Tumor Growth in Mice

Tumor-associated macrophages (TAM) are key regulators of the link between inflammation and cancer, and the interplay between TAM and tumor cells represents a promising target of future therapeutic approaches. We investigated the effect of gallic acid (GA) and caffeic acid (CA) as strong antioxidant and anti-inflammatory agents on tumor growth, angiogenesis, macrophage polarization, and oxidative stress on the angiogenic model caused by the intraperitoneal (ip) inoculation of Ehrlich ascites tumor (EAT) cells (2.5 × 10⁶) in Swiss albino mouse. Treatment with GA or CA at a dose of 40 mg/kg and 80 mg/kg ip was started in exponential tumor growth phase on days 5, 7, 9, and 11. On day 13, the ascites volume and the total number and differential count of the cells present in the peritoneal cavity, the functional activity of macrophages, and the antioxidant and anti-angiogenic parameters were determined. The results show that phenolic acids inhibit the processes of angiogenesis and tumor growth, leading to the increased survival of EAT-bearing mice, through the protection of the tumoricidal efficacy of M1 macrophages and inhibition of proangiogenic factors, particularly VEGF, metalloproteinases -2 and -9, and cyclooxygenase-2 activity.     

Conformational study of the structure of free 12-thiacrown-4 and some of its cation metal complexes

Conformational search of 12-thiacrown-4, 12t4, was performed using the CONFLEX method and the MMFF94S force field whereby 156 conformations were predicted. Optimized geometries of the 156 predicted conformations were calculated at the HF, B3LYP, CAM-B3LYP, M06, M06L, M062x and M06HF levels using the 6-311G** basis set. The correlation energy was recovered at the MP2 level using the same 6-311G** basis set. Optimized geometries at the MP2/6-311G** level and G3MP2 energies were calculated for some of the low energy conformations. The D ₄ conformation was predicted to be the ground state conformation at all levels of theory considered in this work. Comparison between the dihedral angles of the predicted conformations indicated that for the stability of 12t4, a SCCS dihedral angle of 180° requirement is more important than a gauche CSCC dihedral angle requirement. Conformational search was performed also for the 12t4?CAg⁺, Bi³⁺, Cd²⁺, Cu⁺ and Sb³⁺ cation metal complexes using the CONFLEX method and the CAChe-augmented MM3 and MMFF94S force fields. Conformations with relative energies less than 10?kcal/mol at the MP2/6-31+G*//HF/6-31+G* level, with double zeta quality basis set on the metal cations, were considered for computations at the same levels as those used for free 12t4, using also the 6-311G** basis set. The cc-pVTZ-pp basis set was used for the metal cations. The predicted ground state conformations of the 12t4?CAg⁺, Bi³⁺, Cd²⁺, Cu⁺ and Sb³⁺ cation metal complexes are the C ₄, C ₄, C ₄, C _2v and C ₄ conformations, respectively. This is in agreement with the experimental X-ray data for the 12t4?CAg⁺ and Cd²⁺ cation metal complexes, but experimentally by X-ray, the 12t4?CBi³⁺ and Cu⁺ cation metal complexes have C _s and C ₄ structures, respectively.     

Kinetics of the alkaline hydrolysis of isatin and N-methylisatin in water and water-N,N-dimethylacetamide mixtures

The kinetics of amide bond cleavage of isatin and N-methylisatin in the presence of N,N-dimethylacetamide (DMA) was followed spectrophotometrically in the range of solvent composition (0–48.53 wt.%) and temperatures (40–70 °C) using piperidine as a nucleophile. The reaction was studied under pseudo-first-order kinetics. The rate of the reaction decreases largely with increasing organic solvent content. The thermodynamic activation parameters were calculated and discussed in terms of solvation of the activated complex. No linearity was observed between log rate constant and the reciprocal dielectric constant for the solvent used suggesting that there is a selective solvation by higher polar solvent (water). Finally, a mechanism for the ring opening for isatin and N-methylisatin was proposed.     

HPLC-Analysis,Biological Activities and Characterization of Action Mode of Saudi Marrubium vulgare against Foodborne Diseases Bacteria

The present study aims to evaluate the chemical composition, metabolites secondary and pharmacology activities of methanolic extract of Marrubium vulgare collected from King Saudi Arabia. Moreover, the primary mode of action of the tested extract was studied here for the first time against E. coli and L. monocytogenes. HPLC analysis shows that the major components in the tested extract are luteolin-7-O-d-glucoside, ferulic acid and premarrubiin. Obtained data demonstrated that the investigated extract was richer in phenol (26.8 ± 0.01 mg/GAE g) than in flavonoids (0.61 ± 0.05 mg EC/mL). In addition, the methanolic extract showed an important antioxidant capacity against the DPPH (IC₅₀ = 35 ± 0.01 µg/mL) and ABTS (IC₅₀ = 25 ± 0.2 µg/mL) radical scavenging and a strong inhibition of acetylcholinesterase enzyme with an IC₅₀ value corresponding to 0.4 mg/mL. The antibacterial activity demonstrated that the evaluated extract had significant activity against both Gram-positive and Gram-negative bacteria. The effect of time on cell integrity on E. coli and L. monocytogenes determined by time–kill and bacteriolysis tests showed that the M. vulgare extract reduced the viability of both strains after 8 and 10 h and had a bacteriolytic effect against two different categories of bacteria, Gram-positive and negative, which are not of the same potency. Based on obtained data, it can be concluded that Saudi M. vulgare has a high pharmacological importance and can be used in preparation of food or drugs.