The conformational preferences of acylphloroglucinols—a promising class of biologically active compounds

Acylphloroglucinols are a broad class of phloroglucinol derivatives characterized by the presence of a COR group, where R is more often an alkyl chain. They are largely present in natural sources and exhibit a variety of biological activities, including antibacterial, antiviral, antifungal, antitumor, antioxidant, and antimalarial. This work reports the results of a systematic conformational study (in vacuo, chloroform, acetonitrile, and water) of a representative number (118) of actual and model acylphloroglucinol structures, considering the most common R chains and investigating conformational preferences and relative energies as well as the influence of specific structural features characterizing significant subsets of compounds. The study aimed at identifying patterns for conformational preferences and at singling out the conformational aspects more closely related to the individuality of different structures, as these are expected to be more closely linked to the differences in the biological activities of different compounds. The results highlight patterns enabling reliable predictions of the conformational preferences of acylphloroglucinol molecules. © 2012 Wiley Periodicals, Inc.     

Conductance oscillations in a mesoscopic ring threaded by a harmonically time-dependent magnetic flux

We consider a microscopic model for a one-dimensional ring of non-interacting electrons threaded by a magnetic flux of the form Φ(t)=Φ₀+Φ₁cos(Ω₀t)$\Phi (t)={\Phi }_0+{\Phi }_1\cos ({\Omega }_{0}t)$. The ring is attached to two reservoirs at which a bias voltage is applied. We focus on small amplitudes of Φ₁${\Phi }_1$, and we analyze the behavior of the conductance as a function of Φ₀${\Phi }_0$. We solve the problem by means of non-equilibrium Green function techniques.     

Magneto immunofluorescence assay for diagnosis of celiac disease

A magneto immunofluorescence assay for the detection of anti-transglutaminase antibodies (ATG2) in celiac disease was developed. The ATG2 were recognized by transglutaminase enzyme immobilized on the magnetic beads and then the immunological reaction was revealed by antibodies labeled with peroxidase. The fluorescent response of the enzymatic reaction with o-phenylenediamine and H₂O₂ as substrates was correlated with anti-transglutaminase titer, showing EC50 and LOD values of 1:11,600 and 1:74,500 of antibody titers, respectively. A total number of 29 sera samples from clinically confirmed cases of celiac disease and 19 negative control samples were tested by the novel magneto immunofluorescence assay. The data were submitted to the receiver-operating characteristic plot (ROC) analysis which indicated that 8.1 U was the most effective cut-off value to discriminate correctly between celiac and non-celiac patients. The immunofluorescence assay exhibited a sensitivity of 96.6%, a specificity of 89.5% and an efficiency 93.8% compared with the commercial optical ELISA kit.     

Effect of addition of main ion to carrier solution in potentiometric flow-injection measurements with solid state ion-selective electrodes

Summary Flow-injection measurements were performed using chloride, fluoride, iodide and copper(II)-selective electrodes. A pronounced effect of addition of main ion to the carrier solution was observed for the fluoride- and iodide-selective electrode. Super-Nernstian slope observed for the fluoride- and copper(II)-selective electrode in the absence of the sensed ion in the carrier solution decreased to Nernstian values in the presence of the measured ion in the carrier solution. This phenomenon is explained by different response times at different concentrations of the sensed ion.

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Wirkung eines Zusatzes des Hauptions zur Trägerlösung bei potentiometrischen Flow-Injection-Messungen mit ionen-selektiven Festelektroden

     

Purification and Characterization of a Milk Clotting Protease fromMucor bacilliformis

An acid protease having milk clotting activity has been isolated fromMucor bacilliformis cultures. The enzyme was basically purified by ionic exchange chromatography. An average yield of 29 mg purified product was obtained from 100 mL crude extract. As purity criteria, SDS-PAGE, reverse-phase HPLC, and N-terminal analysis were performed. The protease is a protein composed of a single polypeptide chain with glycine at the N-terminus. The mol wt is approx 32,000, and its amino acid composition is very similar to those of other fungal proteases. As expected, its clotting activity was drastically inhibited by pepstatin A action. On the other hand, its instability against heat treatment and its clotting/proteolytic activity ratio indicate that it may be considered as a potential substitute for bovine chymosin. Index Entries:Mucor bacilliformis protease; milk clotting enzyme; acid protease; fungal protease; aspartyl protease.     

Matériaux réactifs à base de collagène

Studies on the functionalisation of collagen by the introduction of polymerisable unsaturated groups, by analogy with the transformation of -OH or -NH₂ groups in proteins using acryloyl chloride as reagent, are presented. These unsaturated groups participate in copolymerisation reactions with vinyl monomers to produce interpenetrating networks. The influence of the parameters temperature, amount of acryloyl chloride and pH on the degree of transformation of the conjunctive protein (evaluated by IR spectroscopy and by dosage of free amine functions) is presented. It was established that pH has a significant influence on the nature of formed bonds (amine or ester type) and on the degree of transformation. Electron microscopy to analyse the products of copolymerisation between functionalised collagen and water-soluble monomers (acrylamide) was used. Interpenetrating networks with complex morphology were observed.     

Indirect determination of iron in a flow-injection system with amperometric detection

The change in peak current resulting from the reaction of Fe(II) with nitroso-R salt in a flow-injection system is used to quantify Fe(II) with either single- or dual-electrode amperometric detectors. The current change varies linearly with Fe(II) concentration from 0 to 200 mg 1^?1. The relative standard deviation was about 5% with the single-electrode detector and about 10% with the dual-electrode detector. The method is evaluated for the determination of iron in dietary supplements.     

Separation of atropisomeric 1,4,5,6-tetrahydropyrimidinium salts by chiral HPLC and determination of their enantiomerization barriers

Chiral HPLC separation of a series of novel atropisomeric quaternary (1) and ternary (2) 1,2-disubstituted 1,4,5,6-tetrahydropyrimidinium salts bearing disymmetric aryl groups in positions 1 and/or 2 is described. A screening of different polysaccharide stationary phases (OD-R, OJ-R and AD-RH) and chromatographic conditions allowed for partial or baseline resolution of 16 over 26 compounds. When a semi-preparative separation was achieved, the corresponding enantiomerization barriers were determined employing the off-column method. The experimental data were compared inter se in order to establish the factors influencing the magnitude of the barriers and with those corresponding to the parent amidines.     

Methodology for predicting the separation of proteins by hydrophobic interaction chromatography and its application to a cell extract

Ligand-exchange micellar electrokinetic capillary chromatography was used for the chiral resolution of underivatized and dansyl amino acid enantiomers simultaneously. The separation was achieved by chiral copper(II)-L-valine complexes incorporated in micelles of sodium dodecyl sulfate (SDS). The enantioresolution was strongly affected by SDS and a concentration of 20 mM SDS was shown to be necessary for the separation. Other impacting factors were investigated including pH, the molar ratio of copper(II) to L-valine and the total concentration of complex. Using the proposed method, 11 different dansyl amino acids and two underivatized amino acids were separated successfully with a running electrolyte of 20 mM NH4OAc, 4 mM CuSO4, 8 mM L-valine and 20 mM SDS at pH 9.0 in less than 25 min. Experiments were also performed with other amino acid ligands in order to vary the stability and the sterical arrangement of the copper(II) complexes and the possible chiral recognition mechanism was also discussed briefly.