Multi-criteria decision making in micellar liquid chromatographic separation of chlorophenols

Simultaneous optimization of separation quality and analysis time of the micellar liquid chromatography of nine chlorophenol isomers was investigated. The effect on retention of three experimental parameters was studied using multivariate analysis. The factors studied were the concentration of sodium dodecyl sulfate, propanol content, and pH of the mobile phase. The experiments were performed according to the face-centered cube central composite design and the inverse form of the experimental retention times of analytes was fitted to polynomial models. The results of the analysis of variance showed that the models obtained explain over 99% of the variance observed in the chromatograms. The good predictive ability of the models was verified by high correlation coefficient (R2 > 0.99) and F ratio values for the plots of predicted cross-validated versus experimental retention times. The study showed that the use of the Pareto-Optimality method, an approach from multi-criteria decision making, allows selection of the best possible combinations of separation quality and analysis time in micellar liquid chromatography of chlorophenols.     

Human genomic DNA analysis using a semi-automated sample preparation, amplification, and electrophoresis separation platform

The growing importance of analyzing the human genome to detect hereditary and infectious diseases associated with specific DNA sequences has motivated us to develop automated devices to integrate sample preparation, real-time PCR, and microchannel electrophoresis (MCE). In this report, we present results from an optimized compact system capable of processing a raw sample of blood, extracting the DNA, and performing a multiplexed PCR reaction. Finally, an innovative electrophoretic separation was performed on the post-PCR products using a unique MCE system. The sample preparation system extracted and lysed white blood cells (WBC) from whole blood, producing DNA of sufficient quantity and quality for a polymerase chain reaction (PCR). Separation of multiple amplicons was achieved in a microfabricated channel 30 microm x 100 microm in cross section and 85 mm in length filled with a replaceable methyl cellulose matrix operated under denaturing conditions at 50 degrees C. By incorporating fluorescent-labeled primers in the PCR, the amplicons were identified by a two-color (multiplexed) fluorescence detection system. Two base-pair resolution of single-stranded DNA (PCR products) was achieved. We believe that this integrated system provides a unique solution for DNA analysis.     

A molecular dynamics investigation on the interaction properties of AzrC and its cofactor

In this report, the main contributions of FMN were employed in the reductive cleavage reaction of AzrC protein (as a member of azoreductase family). Molecular dynamics simulations of three models in the presence and absence of FMN and ligand were performed to gather information about the dynamic nature of active site residues of AzrC. Combination of pairwise decomposition and alanine scanning calculations provides critical information about the FMN binding sites. The MD results analyzed by alanine scanning method revealed the high negative scores for N 10 (A) A, N 12 (A) A, S 17 (A) A and Y 151 (A) A mutations, which were in agreement with pairwise decomposition analyses. Hydrogen bond analyses indicated that these residues play critical roles in establishing appropriate hydrogen bonds between AzrC and FMN. Negative energy results for nonpolar residues such as W 103 (A), M 102 (A) and F 105 (A) and binding free energy analyses of three complexes indicate that the VDW interactions could be regarded as some favorable contribution in FMN and AzrC protein and confirmed the critical role of FMN in ligand binding (35.84 %), in addition to its catalytic function. This information could be used for future experimental investigations.     

An ab initio investigation of chalcogen–hydride interactions involving HXeH as a chalcogen bond acceptor

This work presents an ab initio study on chalcogen–hydride interactions in several binary complexes of chalcogen-containing molecules with HXeH. The geometries, H–Xe stretching frequencies and interaction energies of XCY···HXeH binary complexes are investigated at MP2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels of theory, where X = O, S, Se, Te and Y = S, Se, Te. For each XCY···HXeH complex, a chalcogen–hydride bond is formed between the negatively charged hydrogen atom of the HXeH molecule and the most positive electrostatic potential region (σ-hole) on the surface of the interacting atom Y. Upon complex formation, a notable blue shift is found for the H–Xe stretch vibration. This result reveals that there is a stronger H^?(XeH)⁺ ion-pair character in XCY···HXeH complexes than in free HXeH molecule. In order to shed light on the origin of the chalcogen–hydride interactions, molecular electrostatic potential, quantum theory of atoms in molecules and interaction energy decomposition analyses are performed. Cooperative effects between a conventional chalcogen bond and the chalcogen–hydride interaction in OCY···OCY···HXeH complexes are also investigated.     

Plant-mediated fabrication of cobalt oxide nanoparticles and evaluation of their catalytic effects on electro-oxidation of formaldehyde

Cobalt oxide nanoparticles (Co₃O₄-NPs) were synthesized by aqueous extract of Artemisia vulgaris plant at 50°C. The biosynthesized extract mediated Co₃O₄-NPs were characterized through different methods containing FT-IR (Fourier transform infrared spectroscopy), FESEM (Field emission scanning electron microscopy), EDS (Energy-dispersive x-ray spectroscopy), and XRD (x-ray diffraction). Co₃O₄-NPs as an efficient and practical catalyst was employed for the electrochemical oxidation of formaldehyde; which was an irreversible charge transfer controlled by mass transfer. The coefficients of electron transfer and diffusion were 0.87 and 0.122 cm²/s for formaldehyde oxidation on Co₃O₄ electrode, respectively. The formation of the CoOOH species during potential sweeping appears to be involved in the catalytic activity of the Co₃O₄ toward formaldehyde oxidation.     

PAP inhibitor with in vivo efficacy identified by Candida albicans genetic profiling of natural products

Natural products provide an unparalleled source of chemical scaffolds with diverse biological activities and have profoundly impacted antimicrobial drug discovery. To further explore the full potential of their chemical diversity, we survey natural products for antifungal, target-specific inhibitors by using a chemical-genetic approach adapted to the human fungal pathogen Candida albicans and demonstrate that natural-product fermentation extracts can be mechanistically annotated according to heterozygote strain responses. Applying this approach, we report the discovery and characterization of a natural product, parnafungin, which we demonstrate, by both biochemical and genetic means, to inhibit poly(A) polymerase. Parnafungin displays potent and broad spectrum activity against diverse, clinically relevant fungal pathogens and reduces fungal burden in a murine model of disseminated candidiasis. Thus, mechanism-of-action determination of crude fermentation extracts by chemical-genetic profiling brings a powerful strategy to natural-product-based drug discovery.     

An efficient synthesis of fully substituted pyrazolo[3,4-b]pyridin-5-amines from α-azidochalcones

A facile, mild and efficient procedure for the synthesis of fully substituted pyrazolo[3,4-b]pyridin-5-amines is reported. A mixture of an α-azidochalcone, a 5-aminopyrazole and t-BuOK was stirred in DMF at ambient temperature for 5?min to afford the corresponding pyrazolo[3,4-b]pyridin-5-amines in good to excellent yields.