Alkylsulfanylphenyl derivatives of cytosine and 7-deazaadenine nucleosides, nucleotides and nucleoside triphosphates: synthesis, polymerase incorporation to DNA and electrochemical study

Aqueous Suzuki–Miyaura cross‐coupling reactions of halogenated nucleosides, nucleotides and nucleoside triphosphates derived from 5‐iodocytosine and 7‐iodo‐7‐deazaadenine with methyl‐, benzyl‐ and tritylsufanylphenylboronic acids gave the corresponding alkylsulfanylphenyl derivatives of nucleosides and nucleotides. The modified nucleoside triphosphates were incorporated into DNA by primer extension by using Vent(exo‐) polymerase. The electrochemical behaviour of the alkylsulfanylphenyl nucleosides indicated formation of compact layers on the electrode. Modified nucleotides and DNA with incorporated benzyl‐ or tritylsulfanylphenyl moieties produced signals in [Co(NH₃)₆]³⁺ ammonium buffer, attributed to the Brdi?ka catalytic response, depending on the negative potential applied. Repeated constant current chronopotentiometric scans in this medium showed increased Brdi?ka catalytic response, which suggests the deprotection of the alkylsulfanyl derivatives to free thiols under the conditions.     

Peptidyl-tRNA hydrolase screening combined with molecular docking reveals the antibiotic potential of Syzygium johnsonii bark extract

With the rapid rise of antibiotic resistance in pathogenic bacteria, the need for new antibacterial agents is overwhelming. Herein we report the limited screening of tropical plant extracts for inhibitory activity against the essential enzyme peptidyl-tRNA hydrolase (Pth). Initial screening was conducted through an electrophoretic mobility assay and Northern blot detection. The ability of Pth to cleave the peptide-tRNA ester bond was assessed. The ethanol bark extract of Syzygium johnsonii showed strong inhibitory potential. Molecular docking studies point to Syzygium polyphenolics as the potential source of inhibition. This work is the forerunner of activity-directed isolation, purification, and structure elucidation of the inhibitory components from Syzygium johnsonii extracts and studies of compound interaction with Pth.     

S,N‐Chelated organotin(IV) compounds containing 6‐phenylpyridazine‐3‐thiolate ligand—structural,antibacterial and antifungal study

A series of tri‐ and diorganotin(IV) compounds containing potentially chelating S,N‐ligand(s) (L^SN, where L^SN is 6‐phenylpyridazine‐3‐thiolate) were prepared and structurally characterized by multinuclear NMR spectroscopy. X‐ray diffraction techniques were used for determination of the structure of compounds containing one [(L^SN)Ph₂SnCl], two [(n‐Bu)₂Sn(L^SN)₂] and the combination of two L^SN and one L^CN [(L^CN)(n‐Bu)Sn(L^SN)₂] (where L^CN is {2‐[(CH₃)₂NCH₂]C₆H₄}‐) ligands. The coordination number of the tin atom varies from five to seven and is dependent on the number of chelating ligands present. The formation of the five‐membered azastanna heterocycle is favored over the formation of four‐membered azastannathia heterocycle in compounds containing both types of ligands. The di‐n‐butyl‐substituted compounds are the most efficient ones in inhibition of growth of yeasts, molds and G⁺ bacteria strains. Copyright © 2011 John Wiley & Sons, Ltd.     

Application of the INAA methods for KRISS infant formula CRM analysis: standardization of INAA at KRISS

We have established an instrumental neutron activation analysis (INAA) method, including k₀-based INAA, at the Korea Research Institute of Standards and Science (KRISS) for the certification of reference materials. As part of establishing INAA measurements, KRISS infant formula certified reference material was analysed for multiple elements at three different metrological institutes: KRISS and NIST for the standard comparator method, and JSI for the k₀-INAA method. The mass fraction of most elements was consistent within expanded uncertainty (k?=?2). In addition, the results were used to verify the validity of elemental analysis of Zn using the standard comparator INAA at KRISS, and spreadsheet-based INAA calculations were evaluated.

     

Europium and terbium Schiff base peptide complexes as potential antimicrobial agents against <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Eu(III) and Tb(III) Schiff base complexes are applicable in various fields such as sensing, assays, screening protocols in vitro, and imaging studies in vitro or in vivo. Fluorescent europium and terbium complexes and their interaction with cell penetrating peptide (KKKRKC) can represent an excellent key for understanding pathway of peptide transportation though cell membrane and the application of Schiff base complexes as potential antibacterial drugs. The Schiff base–metal complexes and its conjugates with peptide were tested for their antibacterial activity against Pseudomonas aeruginosa and Salmonella typhimurium. Schiff base–metal complexes conjugated with peptide show minor toxicity in normal human PNT1A cells and high antibacterial activity against P. aeruginosa and S. typhimurium, where IC50 down to 125.9 and/or 36.1 µM were found for P. aeruginosa and S. typhimurium, respectively. Our results strongly suggest that Schiff base–metal complexes conjugated with peptide have great potential to be developed into highly effective antibacterial drug.     

Extraction of polycyclic aromatic nitrogen heterocycles from spiked soil samples

Extraction recovery of 10 selected polycyclic aromatic nitrogen heterocycles (PANHs), quinoline, 2-methylquinoline, 6-methylquinoline, 8-methylquinoline, acridine, benzo[h]quinoline, phenantridine, indole, 2-methylindole, and carbazole from spiked soil samples was tested. Four different extraction techniques, pressurized solvent extraction (PSE), supercritical fluid extraction (SFE), Soxhlet warm extraction (SOXW) and standard Soxhlet extraction (SOX), were applied and compared. The RP-HPLC technique with a silica-based octadecyl stationary phase was used for recovery determination of individual PANHs. Supercritical fluid extraction has been found to be the most effective method for the extraction of selected PANHs from soil. PSE and SOXW methods offered similar results with slightly lower extraction recoveries compared with SFE. On the contrary, SOX is a time-consuming method with a low recovery of target analytes and is not suitable for the extraction of PANHs from soils.     

Comparative Electrochemical and Spectroscopic Studies of I‐Motif‐forming DNA Nonamers

The paper shows the structural diversity of cytosine (C)‐rich oligodeoxynucleotides (ODNs) arising from their detail nucleotide sequence and experimental conditions. In slightly acidic solutions, the ODN nonamers with different adenine (A) and cytosine (C) sequences can adopt non‐canonical structures involving protonated bases. A distinct secondary structure formed in (C)‐rich sequences, called i‐motif (iM), consists of hemiprotonated and intercalated cytosine base pairs (C.C⁺). Folding and unfolding of particular structures in solutions were monitored by ¹H NMR and CD spectroscopies and native polyacrylamide gel electrophoresis (PAGE), which are capable to determine their structural characteristics. Effects of sequences and their proclivity to formation of the iM on electrochemical behaviour of the ODN nonamers were studied by electrochemical methods. The LSV signals of A and C obtained from the reductive dissolution of ODN adsorption layers on a hanging mercury drop electrode were processed by elimination voltammetry with linear scan (EVLS), which revealed complex effects of the nonamer properties (namely their primary and secondary structure confirmed in solution) on their adsorption and reduction activity.     

Dichotomy within 1,4-addition of organolithium and Grignard reagents to α,β-unsaturated Fischer alkoxycarbenes: A new synthesis of Fischer carbenes

The reaction of organolithium and Grignard reagents with pentacarbonyl[(ethoxy)(2-phenylethenyl)carbene]chromium(0) gave, after the quenching of the initially formed product of the 1,4-addition, different products depending on the organometallic and quenching reagents used. The addition of organolithiums, followed by a work-up with acid (AcOH or HCl), afforded the corresponding carbene complexes. In contrast, quenching the reaction mixture with ethanol led to the stereoselective formation of (Z)-enol ethers. The usage of Grignard reagents led to the formation of the carbene complexes regardless of which quenching reagent was used.     

Utilization of Carbon Paste Electrodes for the Voltammetric Determination of Chlortoluron

Conventional (CPE) and miniaturized (m‐CPE) carbon paste electrodes consisting of a carbon paste filled capillary were used for differential pulse voltammetric determination of chlortoluron in samples of river water and soil, in the latter case after the extraction by methanol. Britton‐Robinson buffer pH 3 with low content of methanol was found to be optimal for the determination. The achieved determination limits were 2.8 µmol L^?1 and 0.34 µmol L^?1 in river water, and 3.1 and 4.3 µg g^?1 in soil, using CPE and m‐CPE, respectively.     

Preventing the mixed detergent micelle effect in two‐dimensional electrophoresis on Tris‐Tricine gels

Application of Tris‐N‐[Tris(hydroxymethyl)methyl]glycine gels for 2DE is hampered by formation of mixed CHAPS–SDS micelles resulting in typical swirling pattern in the low mass range, which makes reliable quantitative and qualitative gel evaluation impossible. Modification of 2DE strip equilibration procedure prevented the direct interaction between both detergents during equilibration process, thus substantially improving gel separation.