X-ray,optical, vibrational,electrical, and DFT study of the polymorphic structure of ethylenediammonium bis iodate α-C2H10N2(IO3)2 and β-C2H10N2(IO3)2

The interaction of ethylenediamine with iodic acid by the slow evaporation method at room temperature gives rise to the crystals of α-C₂H₁₀N₂(IO₃)₂ and β-C₂H₁₀N₂(IO₃)₂ denoted as α-EBI and β-EBI, respectively. The acentric crystal structures of both polymorphs that consist of [C₂H₁₀N₂]²⁺ cations and [IO₃]^? anions connected together by N–H…O hydrogen bonds are discussed and compared. The optical properties of both polymorphs were determined using UV-vis diffuse reflectance spectroscopy (DRS) showing a wide transparency windows. The DFT calculations using the mixed B3PW91/[6–31?+?(d, p), LanL2Dz] basis set of optimized geometries, dipole moment (μ), polarizability (α), first static hyperpolarizability (β), and population analysis were also reported. The experimental and theoretical IR and Raman spectra were compared, and the careful and complete assignment of the vibrational motions of both compounds was undertaken with the aid of potential energy distribution (PED) analysis. DSC and AC conductivity analysis revealed that α-C₂H₁₀N₂(IO₃)₂ and β-C₂H₁₀N₂(IO₃)₂ undergo a first-order phase transition around 360 K. The electrical σ_tot (ω, T) conductivity obeyed to Jonscher’s power law and the temperature dependence of the S(T) parameter showed that the electrical conductivity of both polymorph phases might be treated using the correlated barrier hopping (CBH) model.

     

AUTOINDUCTION AND ALDEHYDE CHAIN-LENGTH EFFECTS ON THE BIOLUMINESCENT EMISSION FROM THE YELLOW PROTEIN ASSOCIATED WITH LUCIFERASE IN Vibrio fischeri STRAIN Y-1b

Abstract— A new strain of the yellow-light emitting bacterium Vibrio fischeri Y-lb, possessing a higher fraction of its emission in the yellow, was isolated and characterized. The in vivo yellow to blue ratio (Y/B) increases during growth in parallel with the autoinduction of luciferase, reaching a value above 5 at 17°C. This Y/B increase is attributed to concomitant increases in the intracellular levels of both luciferase and the specific protein associated with yellow emission, the yellow fluorescent protein (YFP), and to the association of the two proteins at higher concentrations. The yellow emission is rapidly but reversibly lost by brief exposures to a temperature of 27°C (5 s), and irreversibly so at 40°C, attributed to dissociation of the two proteins. A concentrated crude extract emits almost exclusively yellow light in the in vitro reaction, and theY/B ratio decreases with dilution. The Y/B ratio in vitro is also dependent on the aldehyde chain length; experiments with aldehyde analogs suggest that the aldehyde binding site of luciferase must be occupied for YFP to stimulate light emission.     

Graphene CVD growth on copper and nickel: role of hydrogen in kinetics and structure

Understanding the chemical vapor deposition (CVD) kinetics of graphene growth is important for advancing graphene processing and achieving better control of graphene thickness and properties. In the perspective of improving large area graphene quality, we have investigated in real-time the CVD kinetics using CH(4)-H(2) precursors on both polycrystalline copper and nickel. We highlighted the role of hydrogen in differentiating the growth kinetics and thickness of graphene on copper and nickel. Specifically, the growth kinetics and mechanism is framed in the competitive dissociative chemisorption of H(2) and dehydrogenating chemisorption of CH(4), and in the competition of the in-diffusion of carbon and hydrogen, being hydrogen in-diffusion faster in copper than nickel, while carbon diffusion is faster in nickel than copper. It is shown that hydrogen acts as an inhibitor for the CH(4) dehydrogenation on copper, contributing to suppress deposition onto the copper substrate, and degrades quality of graphene. Additionally, the evidence of the role of hydrogen in forming C-H out of plane defects in CVD graphene on Cu is also provided. Conversely, resurfacing recombination of hydrogen aids CH(4) decomposition in the case of Ni. Understanding better and providing other elements to the kinetics of graphene growth is helpful to define the optimal CH(4)/H(2) ratio, which ultimately can contribute to improve graphene layer thickness uniformity even on polycrystalline substrates.     

The application of "double isolation" in Fourier transform ion cyclotron resonance sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry to remove labile isobaric impurities

This study reports the application of "double isolation" in sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry (SORI-CID-MS/MS) to remove radio- frequency (RF) fragment ions of very close mass isobaric ions (0.02 m/z apart). Analyses were performed with a fraction of a biological extract isolated from a macroalgae containing the mycosporine-like amino acid asterina-330. Direct isolation of the precursor ion by narrowing the isolation window proved ineffective as it impinged upon the required ion thus substantially reducing its intensity. By increasing the correlated sweep time, ejection efficiency of the isolation was improved, but caused the unwanted side-effect of RF fragmentation of labile ions. Finally, by skipping the ion activation step and performing a second isolation (in the MS(3) module) the RF fragments from the first isolation were removed leaving a very pure isolation of the required precursor ion and allowed a very clean CID fragmentation. We demonstrated that the m/z 272.1351 ion is derived from the loss of NH(3) from m/z 289.1620 isobaric impurity and is not related to asterina-330. This application represents a powerful tool to remove unwanted ions in the MS/MS spectrum that result from fragmentation of isobaric ions.     

Characterization of the aeolian aerosol from Cape Verde by k 0-INAA and PIXE

Due to its location on West Coast of Africa, Cape Verde is highly influenced by Sahara Desert dust events being an optimum place to observe and study the African aeolian aerosol. During 2011, particulate matter with an aerodynamic diameter lower than 10 μm (PM₁₀) was sampled in Santiago Island and its chemical composition was evaluated by k ₀-instrumental neutron activation analysis (k ₀-INAA) and particle induced X-ray emission (PIXE). This study showed the existence of a seasonal intrusion of dust from Africa (that occurred from October to March) characterized by significant increases of PM₁₀, mineral elements and anthropogenic particles concentrations. In 2011, the PM₁₀ health-based air quality guidelines defined by WHO, EU and USEPA were exceeded. Cape Verde PM₁₀ composition was characterized essentially by high concentrations of elements originating from the soil (Ca, Ce, Co, Fe, K, Mg, Mn, Rb, S, Sc, Si, Sm, and Ti) and sea (Br, Cl, and Na); and low concentrations of anthropogenic elements (As, Cr, Cu, Ni, Pb, Sb, V, and Zn). k ₀-INAA and PIXE were fundamental tools for the determination of airborne chemical elements in Cape Verde. Their multi-elemental capabilities in association with low detection limits made it possible to determine the majority of the element concentrations of environmental interest.     

Letter: radical ion and protonated molecule formation with retinal in electrospray and nanospray

This paper reports a preliminary study of the nanospray ionisation mass spectrometry analyses of retinoic acid and retinal. The results are compared and contrasted to the results normally observed with electrospray ionisation. A significant difference in behaviour was observed for the balance between radical ion formation and protonated molecule formation for retinal. The results suggest that the influence of the very different ionisation conditions present in nanospray is very important in determining how ionisation is achieved and has potentially wide ranging applications in the fields of mass spectral analysis of biological and medical extracts.     

Tandem Transesterification–Esterification Reactions Using a Hydrophilic Sulfonated Silica Catalyst for the Synthesis of Wintergreen Oil from Acetylsalicylic Acid Promoted by Microwave Irradiation

SiO₂–SO₃H, with a surface area of 115 m²/g and pore volume of 0.38 cm³g⁻¹, and 1.32 mmol H⁺/g was used as a 20% w/w catalyst for the preparation of methyl salicylate (wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor over 40 min at 120 °C in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be reused three times.