[N‐(6‐Amino‐3,4‐di­hydro‐3‐methyl‐5‐nitroso‐4‐oxopyrimidin‐2‐yl)glycylglycinato]aquapotassium,a three‐dimensional coordination polymer

In the title compound, polymeric potassium N‐(6‐amino‐3,4‐di­hydro‐3‐methyl‐5‐nitro­so‐4‐oxopyrimidin‐2‐yl)­glycyl­gly­cinate hydrate, (K⁺·C₉H₁₁N₆O₅^?·H₂O)_n, the hexacoordinate K⁺ cation is linked to five different anions as well as to the water mol­ecule, with K—O distances in the range 2.617 (2)–2.850 (2) Å. Four of the O atoms in each anion coordinate to K centres, one of them acting as a bridging ligand, leading to the formation of nearly square centrosymmetric K₂O₂ rings. The structure is analysed in terms of (010) metal–ligand sheets linked by [010] chains of fused rings.     

The Addition of Microencapsulated or Nanoemulsified Bioactive Compounds Influences the Antioxidant and Antimicrobial Activities of a Fresh Cheese

The objective of this study was to compare the effects of the incorporation of microcapsules or nanoemulsions with Opuntia oligacantha on the quality of fresh cheese. Three treatments were established: Control, cheese with microcapsules (Micro), and cheese with nanoemulsion (Nano). The parameters evaluated were physicochemical (moisture, ash, fat, proteins, and pH), microbiological (mesophilic aerobic bacteria, mold–yeast, and total coliforms), functional (total phenols, flavonoids, and antioxidant capacity), and texture (hardness, elasticity, cohesion, and chewiness) during storage for 45 days at 4 °C. The results showed that adding microcapsules and nanoemulsion did not affect the physicochemical parameters of the cheese. Total coliforms decreased in all samples from the first days of storage (Control: 4.23 ± 0.12, Micro: 3.27 ± 0.02, and Nano: 2.68 ± 0.08 Log10 CFU), as well as aerobic mesophiles and mold–yeast counts. Regarding the functional properties, an increase in total phenols was observed in all treatments. The texture profile analysis showed that the addition of microcapsules and nanoemulsion influenced hardness (Control: 8.60 ± 1.12, Micro: 1.61 ± 0.31, and Nano: 3.27 ± 0.37 N). The antimicrobial effect was greater when nanoemulsions were added, while adding microcapsules influenced the antioxidant activity more positively.     

Extreme inaccuracies in Gaussian Bayesian networks

To evaluate the impact of model inaccuracies over the network’s output, after the evidence propagation, in a Gaussian Bayesian network, a sensitivity measure is introduced. This sensitivity measure is the Kullback-Leibler divergence and yields different expressions depending on the type of parameter to be perturbed, i.e. on the inaccurate parameter.In this work, the behavior of this sensitivity measure is studied when model inaccuracies are extreme, i.e. when extreme perturbations of the parameters can exist. Moreover, the sensitivity measure is evaluated for extreme situations of dependence between the main variables of the network and its behavior with extreme inaccuracies. This analysis is performed to find the effect of extreme uncertainty about the initial parameters of the model in a Gaussian Bayesian network and about extreme values of evidence. These ideas and procedures are illustrated with an example.     

Synthesis of diazatricyclic core of Madangamines from cis-perhydroisoquinolines

Synthesis of the tricyclic core of madangamine alkaloids has been achieved in a 10-step sequence starting from a 4-(aminomethyl)anisole derivative. A Birch reduction and acylation with cyanoacetic acid followed by an intramolecular Michael process renders a polyfunctionalized cis-perhydroisoquinoline. A diastereoselective allylation and reduction of amide, nitrile, and ketone groups leads to a bicyclic alcohol, which undergoes aminocyclization through the nosyl derivative to the diazatricyclic ring.     

Determination of beta-carboline alkaloids in foods and beverages by high-performance liquid chromatography with electrochemical detection at a glassy carbon electrode modified with carbon nanotubes

Simple and sensitive methods for the separation and quantification of β-carboline alkaloids in foods and beverages by HPLC with electrochemical detection at carbon nanotubes-modified glassy carbon electrodes (CNTs-GCE) are reported. Electrode modification with multi-wall CNTs produced an improved amperometric response to β-carbolines, in spite of the working medium consisting of methanol:acetonitrile: 0.05 mol L⁻¹ Na₂HPO₄ solution of pH 9.0 (20:20:60). On the contrary to that observed at a bare GCE, a good repeatability of the amperometric measurements carried out at +900 mV versus Ag/AgCl (R.S.D. of 3.2% for i_p, n = 20) was achieved at the CNTs-GCE. Using an Ultrabase C₁₈ column and isocratic elution with the above mentioned mobile phase, a complete resolution of the chromatographic peaks for harmalol, harmaline, norharmane, harmane and harmine, was achieved. Calibration graphs over the 0.25-100 μM range with detection limits ranging between 4 and 19 ng mL⁻¹, were obtained. The HPLC-ED at CNTs-GCE method was applied to the analysis of beer, coffee and cheese samples, spiked with β-carbolines at concentration levels corresponding to those may be found in the respective samples. The steps involved in sample treatment, such as extraction and clean-up, were optimized for each type of sample. Recoveries ranging between 92 and 102% for beer, 92 and 101% for coffee, and 88 and 100% for cheese, at sub-μg mL⁻¹ or g⁻¹ analytes concentration levels were achieved.     

Alkoxy-substituted difluoroboron benzoylmethanes for photonics applications: a photophysical and spectroscopic study

Two series of novel boron difluoride adducts (BDFs), namely [BF(2)(OO(R(n)))] (type I) and [BF(2)(OO(2R(n)))] (type II) (R = C(6)H(4)OC(n)H(2n+1); n = 10-18), containing β-diketonate ligands bearing 4-alkoxyphenyl substituents in position 1 or in positions 1,3 of the β-diketonate core, respectively, have been prepared. All of them display a strong interaction between the ligand and the BF(2) group, as deduced from the IR spectroscopic data, and strong blue-violet emission (λ(em)(max) from 400 to 440 nm), with fluorescence quantum yields from 0.69 to 0.84 (type I) and 0.48 to 0.66 (type II) and fluorescence lifetimes of 1.7 and 2.2 ns in diluted dichloromethane solution, respectively. The photophysical properties of I and II series of dyes are independent of the solvent polarity and the chain length of the alkoxyphenyl substituent(s). Moreover, they exhibit high photostability even under intense laser light. Contradicting previous interpretations, our detailed photophysical and spectroscopic study rules out excimer formation even in highly concentrated solution or in the solid state, demonstrating the resistance of these dyes to self-aggregation. All those features pave the way to the application of such fluorophores in OLEDs, solid dye lasers, chemical sensors and two-photon biological labels, to name a few.