Comparison in practical applications of crown ether sensor molecules containing an acridone or an acridine unit – a study on protonation and complex formation

Crown ethers containing an acridone or an acridine unit are successfully applied opto- and electrochemical cation sensors. The heteroaromatic unit of these macrocycles can be in different forms during the applications, which have a strong influence on the sensing behavior. Moreover, in the case of acridono-macrocycles a prototropic equilibrium takes place upon complexation, which is effected by the physicochemical characteristics. A Pb2+-selective acridono-18-crown-6 ether and its 9-phenylacridino-analogue were used as model compounds for comparing the different forms of the heterocyclic units of these sensor molecules. Since in most practical sensor applications of the fluorescent hosts a non-neutral aqueous medium is present, studies on complexation and signaling were carried out from the aspect of the relationship among protonation, coordinating ability, complex stability and tautomeric equilibrium. A strong interdependence among these factors was found and limitations of using unsubstituted acridino- and acridono-sensor molecules in comparison with their 9-substituted-acridino-analogues were discussed. This study will hopefully serve as a useful standpoint for future development of ionophore-based sensors containing an acridone or an acridine unit.

Fluorometric sensing of hydroxylamine in an aqueous medium utilizing a diphenyl imidazole-based probe

A diphenyl imidazole-based probe for highly selective fluorometric sensing of hydroxylamine in a neutral aqueous medium.

Soluble Colloidal Manganese Dioxide: Formation, Characterization and Application in Oxidative Kinetic Study of Ciprofloxacin

Soluble colloidal manganese dioxide was formed by reduction of potassium permanganate with sodium thiosulphate in neutral aqueous medium at 25 ºC. The obtained nano-sized colloidal manganese dioxide was found to be dark reddish-brown in color and stable for several months. The formation of manganese dioxide was confirmed by UV-visible spectrophotometer and determination of oxidation state of Mn species in manganese dioxide. The effect of different concentration of sodium thiosulphate on the formation of manganese dioxide was also studied. The nano-sized colloid manganese dioxide was characterized by transmission electron microscopy and Fourier transform infrared spectrophotometer. The formed soluble colloidal manganese dioxide was used as an oxidant in oxidation of ciprofloxacin in perchloric acid medium at 35 ºC. The reaction was first-order concerning to concentration of manganese dioxide and hydrogen ion but fractional order with ciprofloxacin. The results suggest formation of complex between ciprofloxacin and manganese dioxide. The oxidation products were also identified based on stoichiometric and characterization results. Copyright © 2020 BCREC Group. All rights reserved

Tri-Cyclic Nucleobase Analogs and their Ribosides as Substrates of Purine-Nucleoside Phosphorylases. II Guanine and Isoguanine Derivatives

Etheno-derivatives of guanine, O6-methylguanine, and isoguanine were prepared and purified using standard methods. The title compounds were examined as potential substrates of purine-nucleoside phosphorylases from various sources in the reverse (synthetic) pathway. It was found that 1,N2-etheno-guanine and 1,N6-etheno-isoguanine are excellent substrates for purine-nucleoside phosphorylase (PNP) from E. coli, while O6-methyl-N2,3-etheno-guanine exhibited moderate activity vs. this enzyme. The latter two compounds displayed intense fluorescence in neutral aqueous medium, and so did the corresponding ribosylation products. By contrast, PNP from calf spleens exhibited only modest activity towards 1,N6-etheno-isoguanine; the remaining compounds were not ribosylated by this enzyme. The enzymatic ribosylation of 1,N6-etheno-isoguanine using two forms of calf PNP (wild type and N243D) and E. coli PNP (wild type and D204N) gave three different products, which were identified on the basis of NMR analysis and comparison with the product of the isoguanosine reaction with chloroacetic aldehyde, which gave an essentially single compound, identified unequivocally as N9-riboside. With the wild-type E. coli enzyme as a catalyst, N9--d- and N7--d-ribosides are obtained in proportion ~1:3, while calf PNP produced another riboside, tentatively identified as N6--d-riboside. The potential application of various forms of PNP for synthesis of the tri-cyclic nucleoside analogs is discussed.

Anti Corrosion Ability and Biocidal Efficiency of Surfactants on Mild Steel in Aqueous Environment

<div><p><em>The inhibition efficiency of DMBP (Diethyl-4-methyl benzyl phosphonate) along with Biocidal action of CTAB and SDS on corrosion of mild steel in neutral aqueous medium has been evaluated by mass loss method, both in absence and presence of Zn²⁺. It is observed that DMBP exhibits 65% IE individually at ambient temperature. Synergistic influence of Zn²⁺ increases IE of DMBP to 71%. Addition of surfactants CTAB (N-Cetyl-N,N,N-Trimethyl Ammonium Bromide) and SDS ( Sodium dodecyl Benzene sulphonate) enhances the inhibition efficiency of DMBP from 65% to 96% and 92% respectively. The inhibitor system consisting of DMBP (200 ppm) + Zn²⁺ (90 ppm)+ CTAB (50 ppm) / SDS (40 ppm) offered maximum Biocidal efficiency (BE %) of 100% after killing of microbial bacteria present in aqueous system. FTIR spectra indicates the protective film consist of Fe²⁺-DMBP and Zn(OH)₂.</em></p></div>