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The intracellular ability of the "10-23" DNAzyme to efficiently inhibit expression of targeted proteins has been evidenced by in vitro and in vivo studies. However, standard conditions for kinetic measurements of the DNAzyme catalytic activity in vitro include 25 mM Mg[sup 2+], a concentration that is very unlikely to be achieved intracellularly. To study this discrepancy, we analyzed the folding transitions of the 10-23 DNAzyme induced by Mg[sup 2+]. For this purpose, spectroscopic analyzes such as fluorescence resonance energy transfer, fluorescence anisotropy, circular dichroism, and surface plasmon resonance measurements were performed. The global geometry of the DNAzyme in the absence of added Mg[sup 2+] seems to be essentially extended, has no catalytic activity, and shows a very low binding affinity to its RNA substrate. The folding of the DNAzyme induced by binding of Mg[sup 2+] may occur in several distinct stages. The first stage, observed at 0.5 mM Mg[sup 2+], corresponds to the formation of a compact structure with limited binding properties and without catalytic activity. Then, at 5 mM Mg[sup 2+], flanking arms are projected at right position and angles to bind RNA. In such a state, DNAzyme shows substantial binding to its substrate and significant catalytic activity. Finally, the transition occurring at 15 mM Mg[sup 2+] leads to the formation of the catalytic domain, and DNAzyme shows high binding affinity toward substrate and efficient catalytic activity. Under conditions simulating intracellular conditions, the DNAzyme was only partially folded, did not bind to its substrate, and showed only residual catalytic activity, suggesting that it may be inactive in the transfected cells and behave like antisense oligodeoxynucleotide. [ABSTRACT FROM AUTHOR]

Five ruthenium(II) half-sandwich complexes containing arene and coumarin ligands with the general formula [Ru(arene)(L)Cl 2 ] or [Ru(arene)(L 2 )Cl]Cl were synthesized. L: 3-aminocoumarin and 7-amino-4-methylcoumarin were used for the synthesis of complex compounds. The complexes were characterized by 1 H NMR, IR, UV–Vis spectroscopy, electrospray mass spectrometry (ESI MS), elemental analysis and cyclic voltammetry measurement. X-ray crystallography found one molecular structure to be of pseudo-octahedral geometry. All compounds were also tested on Chronic Myelogenous Leukemia (K562), Human Cervix Carcinoma (HeLa), Human Pancreatic Carcinoma (CFPAC) cancer cell lines, and the viability of cells was evaluated by MTT assay. [ABSTRACT FROM AUTHOR]

Abstract: Efficient Pd(0)-catalysed synthesis of 5-alkynyl-1-β-d-ribofuranosyl-1H-[1,2,3]triazole-4-carboxylic acid amide depends on the presence of different protecting groups of the ribose moiety. Peracetylated 5-iodo substrate (15) couples with terminal alkynes or trimethyl-[(tributylstannyl)ethynyl]silane in 50–71% and 72% yield (ETCAR), respectively, although its hydrodehalogenation to 19 is noticeable. On the other hand, hydrodehalogenation of acetonide (16) predominates over coupling with terminal alkyne and slightly decreases a yield of cross-coupling reaction with trimethyl[(tributylstannyl)ethynyl]silane. Alternative conditions of reaction with terminal alkynes, to exclude so far identified hydride sources to produce hydridopalladium species, have been established for acetonide 16 and allowed to achieve 72% of coupling. Fluoromethyl derivative (42) was prepared from its 5-hydroxymethyl precursor by fluorination with DAST. Additionally, X-ray structural analysis of 42 was performed. All 1,2,3-triazolonucleosides and two synthesized cycloSal-pronucleotides were evaluated for cytotoxic activity against K562, HeLa and HUVEC cells. [Copyright &y& Elsevier]

Hydrazone hesperetin Schiff base (HHSB) — N-[(±)-[5,7-dihydroxy-2-(3-hydroxy-4-methoxy-phenyl)chroman-4-ylidene]amino]benzamide has been synthesized and its crystal structure was determined. This compound was used for the formation of Cu(II) complexes in solid state and in solution which were characterized using different spectroscopic methods. The analyses of potentiometric titration curves revealed that monomeric and dimeric complexes of Cu(II) are formed above pH 7. The ESI–MS (electrospray ionization–mass spectrometry) spectra confirmed their formation. The EPR and UV–visible spectra evidenced the involvement of oxygen and nitrogen atoms in Cu(II) coordination. Hydrazone hesperetin Schiff base can show keto-enol tautomerism and coordinate Cu(II) in the keto (O − , N, O ket ) and in the enolate form (O − , N, O − enol ). The semi-empirical molecular orbital method PM6 and DFT (density functional theory) calculations have revealed that the more stable form of the dimeric complex is that one in which the ligand is present in the enol form. The CuHHSB complex has shown high efficiency in the cleavage of plasmid DNA in aqueous solution, indicating its potential as chemical nuclease. Studies on DNA interactions, antimicrobial and cytotoxic activities have been undertaken to gain more information on the biological significance of HHSB and copper(II)–HHSB chelate species. [ABSTRACT FROM AUTHOR]

Abstract: Gemcitabine (dFdC) is a cytidine analog remarkably active against a wide range of solid tumors. Inside a cell, gemcitabine is phosphorylated by deoxycytidine kinase to yield gemcitabine monophosphate, further converted to gemcitabine di- and triphosphate. The most frequent form of acquired resistance to gemcitabine in vitro is the deoxycytidine kinase deficiency. Thus, proper prodrugs carrying the 5′-pdFdC moiety may help to overcome this problem. A series of new derivatives of gemcitabine possessing N-acyl(thio)phosphoramidate moieties were prepared and their cytotoxic properties were determined. N-Acyl-phosphoramidate derivatives of gemcitabine have similar cytotoxicity as gemcitabine itself, and have been found accessible to the cellular enzymes. The nicotinic carboxamide derivative of gemcitabine 5′-O-phosphorothioate occurred to be the best inhibitor of bacterial DNA polymerase I and human DNA polymerase α. [Copyright &y& Elsevier]