Supramolecular hydrogen‐bonded networks in adeninediium hemioxalate chloride and adeninium semioxalate hemi(oxalic acid) monohydrate

In 9H‐adenine‐1,7‐diium hemioxalate chloride, C₅H₇N₅²⁺·0.5C₂O₄²⁻·Cl⁻, (I), adenine is doubly protonated, while in 7H‐adenin‐1‐ium semioxalate hemi(oxalic acid) monohydrate, C₅H₆N₅⁺·C₂HO₄⁻·0.5C₂H₂O₄·H₂O, (II), adenine and one oxalate anion are both monoprotonated. In (I), the adeninium cation forms R₂²(8) and R₁²(5) hydrogen‐bonding motifs with the centrosymmetric oxalate anion, while in (II), the cation forms R₂¹(6) and R₁²(5) motifs with the centrosymmetric oxalic acid molecule and R₁²(5)and R₂²(9) motifs with the monoprotonated oxalate anion. Linear hydrogen‐bonded trimers are observed in (I) and (II). In both structures, the hydrogen bonds lead to the formation of two‐dimensional supramolecular hydrogen‐bonded sheets in the crystal packing. The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds and the diversity seen in the supramolecular hydrogen‐bonded networks as a result of such interactions.     

Admittance as a useful tool for investigation of solute–solvent interactions at the double layer

The application of admittance measurements, an often neglected topic in impedance spectroscopy, to further our understanding of solute–solvent interactions at the double layer is presented by comparing aqueous solutions of sodium acetate and protonated lidocaine acetate. Unlike impedance, the overlap of concentration-dependent hydration cospheres and the potential- and frequency-dependent orientation effects of water molecules around the ions at or near the double layer could be manifested in admittance data. Admittance, but not impedance, also allows identification of interactions between two dipoles, such as amino and carbonyl groups, by changing frequencies and applied potentials. The effects manifest themselves by exhibiting cathodic and anodic shifts with frequency changes. All the admittance data could be reasonably explained by utilizing the concept of “potential induced and water structure-enforced ion-pair formation”.     

Correlating the Electrochemical Kinetics of Myoglobin‐Films to pH Dependent Meat Color

We report here for the first time application of electrochemical kinetics to understand the myoglobin redox‐properties at three relevant meat pH conditions. We investigated the kinetics of oxymyoglobin formation electrochemically using films of myoglobin coated on high‐purity graphite electrodes. Three pH conditions corresponding to the physiological state (pH 7.4), stressed animal muscle (pH 6.4), and post‐mortem meat (pH 5.6) were examined in this study. Our findings show that slower metmyoglobin reduction rate and diminished oxygen‐affinity cause the discoloration of red‐meat at low acidic pH‐conditions in comparison to the physiological pH 7.4.     

Theoretical investigation on the binding specificity of fluorinated sialyldisaccharides Neu5Acα(2–3)Gal and Neu5Acα(2–6)Gal with influenza hemagglutinin H1 – A Molecular Dynamics Study

In the present study, the hydroxyl groups at the C4 and C7 positions of sialic acid and C6 position of galactose in Neu5Acα(2–3)Gal (N23G) and the hydroxyl groups at the C8 position of sialic acid and C3 and C4 positions of galactose in Neu5Acα(2–6)Gal (N26G) were substituted with fluorine atoms, respectively. Molecular dynamics simulations of 100 ns duration were carried out to investigate the structural and dynamical behavior of H1 bound with the tri-fluorinated N23G and N26G (FN23G and FN26G). Based on energy analysis, it was concluded that FN26G should be a better binder for hemagglutinin (H1) than FN23G and it might act as an inhibitor for influenza.     

Measurement of high-power microwave pulse under intense electromagnetic noise

KALI-1000 pulse power system has been used to generate single pulse nanosecond duration high-power microwaves (HPM) from a virtual cathode oscillator (VIRCATOR) device. HPM power measurements were carried out using a transmitting-receiving system in the presence of intense high frequency (a few MHz) electromagnetic noise. Initially, the diode detector output signal could not be recorded due to the high noise level persisting in the ambiance. It was found that the HPM pulse can be successfully detected using wide band antenna, RF cable and diode detector set-up in the presence of significant electromagnetic noise. Estimated microwave peak power was ∼59.8 dBm (∼1 kW) at 7 m distance from the VIRCATOR window. Peak amplitude of the HPM signal varies on shot-to-shot basis. Duration of the HPM pulse (FWHM) also varies from 52 ns to 94 ns for different shots.     

A novel series of anthraquinone-based discotic liquid crystals with bulky substituents: synthesis and characterization

A novel series of anthraquinone-based discotic liquid crystals with bulky substituents, namely 1,5-dibenzyloxy-2,3,6,7-tetraalkyloxy-9,10-anthraquinones, has been synthesized starting from gallic acid. This is, to our knowledge, the first example of bulky substitution in a discotic C₂-symmetric molecule forming columnar phases. Except for the lowest homologue, all members of this series are found to exhibit columnar mesophases; the low temperature mesophase appears to be three-dimensionally ordered whereas the high temperature mesophase is hexagonal columnar (Col_h). We find that the introduction of benzyl substituents for alkyl chains (in the 1,5-positions) on the anthraquinone hexaalkoxylates stabilizes the three-dimensionally ordered phase, whereas it destabilizes the Col_h phase, compared with the anthraquinone hexaalkoxylates. Interestingly, the three-dimensionally ordered phase extends down to -50 °C, making these new derivatives suitable for device applications.     

Comments on Some Recent Results on Controllability of Abstract Differential Problems

In this note we comment on some recent papers treating exact controllability of abstract control problems with a linear part dominated by a sectorial operator.