An Optimized Synthesis, Molecular Structure and Characterization of Benzylic Derivatives of 1,2,4-Triazin-3,5(2H,4H)-dione.

4-Benzyl-1,2,4-triazin-3,5(2H,4H)-dione (3-benzyl-6-azauracil, 2), and 2,4-dibenzyl-1,2,4-triazin-3,5(2H,4H)-dione (1,3-dibenzyl-6-azauracil, 3) were synthesized by the reaction of 1,2,4-triazin-3,5(2H,4H)-dione (6-azauracil, 1) with benzyl bromide and potassium carbonate in dry acetone via the 18-crown-6-ether catalysis. In these reaction methods, we developed more convenient and efficient methodologies to afford compounds 2 and 3 in good yields. These compounds were characterized by ¹H- and 13C-NMR, MS spectrum, IR spectroscopy and elemental analysis. The structure of 2 was verified by 2D-NMR measurements, including gHSQC and gHMBC measurements. A single-crystal X-ray diffraction experiment indicated that compound 3, with the molecular formula C17H15N3O2, crystallized from a CH3OH/CH2Cl2 diffusion solvent system in a monoclinic space group P21/c with a = 13.7844(13), b = 8.5691(8), c = 13.0527(12) Å, ß = 105.961(2)°, V = 1482.3(2) ų, Z = 4, resulting in a density Dcalc of 1.314 g/cm³. The crystal structure of compound 3 is tightly stabilized by contact with five other molecules from the six short contacts formed by intermolecular C-O···H-Car, C-H···Car, and weakly π···π stacking interactions. The dihedral angle 31.90° is formed by the mean planes of the benzene rings of the N-2 and N-4 benzyl groups.

Au(I)-catalyzed and iodine-mediated cyclization of enynylpyrazoles to provide pyrazolo[1,5-a]pyridines.

Pyrazolo[1,5-a]pyridines and 6-iodopyrazolo[1,5-a]pyridines were synthesized by gold-catalyzed and iodine-mediated cyclization of enynylpyrazoles in good to excellent yields, respectively. The iodinated adducts were further converted to 6-arylpyrazolo[1,5-a]pyridines via Suzuki-Miyaura coupling reaction and 6-cyanopyrazolo[1,5-a]pyridine by Ullmann condensation reaction. One of the cyclization adducts, 2-(4-fluorophenyl)pyrazolo[1,5-a]pyridine, was converted to a p38 kinase inhibitor, 2-(4-fluorophenyl)-3-(4-pyridinyl)pyrazolo[1,5-a]pyridine, in two steps.

In vitro selection and characterization of a novel Zn(II)-dependent phosphorothiolate thiolesterase ribozyme.

Here we present the in vitro selection of a novel ribozyme specific for Zn2+-dependent catalysis on hydrolysis of a phosphorothiolate thiolester bond. The ribozyme, called the TW17 ribozyme, was evolved and selected from an artificial RNA pool covalently linked to a biotin-containing substrate through the phosphorothiolate thiolester bond. The secondary structure for the evolved ribozyme consisted of three major helices and three loops. Biochemical and chemical studies of ribozyme-catalyzed reaction products provided evidence that the ribozyme specifically catalyzes hydrolysis of the phosphorothiolate thiolester linkage. A successful ribozyme construct with active catalysis in trans further supported the determined ribozyme structure and indicated the potential of the ribozyme for multiple-substrate turnover. The ribozyme also requires Zn2+ and Mg2+ for maximal catalysis. The TW17 ribozyme, in the presence of Zn2+ and Mg2+, conferred a rate enhancement of at least 5 orders of magnitude when compared to the estimated rate of the uncatalyzed reaction. The ribozyme completely lost catalytic activity in the absence of Zn2+, like Zn2+-dependent protein hydrolases. The discovery and characterization of the TW17 ribozyme suggest additional roles for Zn2+ in ribozyme catalysts.

A copper-mediated cyclization reaction of hydrazine with enediynones providing pyrazolo[1,5-a]pyridines.

2,7-Disubstituted pyrazolo[1,5-a]pyridines were synthesized in good chemical yields by the reaction of enediynones with hydrazine, followed by addition of copper chloride. This reaction can tolerate many functional groups.

Versatile phosphoramidation reactions for nucleic acid conjugations with peptides, proteins, chromophores, and biotin derivatives.

Chemical conjugations of nucleic acids with macromolecules or small molecules are common approaches to study nucleic acids in chemistry and biology and to exploit nucleic acids for medical applications. The conjugation of nucleic acids such as oligonucleotides with peptides is especially useful to circumvent cell delivery and specificity problems of oligonucleotides as therapeutic agents. However, current approaches are limited and inefficient in their ability to afford peptide-oligonucleotide conjugates (POCs). Here, we report an effective and reproducible approach to prepare POCs and other nucleic acid conjugates based on a newly developed nucleic acid phosphoramidation method. The development of a new nucleic acid phosphoramidation reaction was achieved by our successful synthesis of a novel amine-containing biotin derivative used to systematically optimize the reactions. The improved phosphoramidation reactions dramatically increased yields of nucleic acid-biotin conjugates up to 80% after 3 h reaction. Any nucleic acids with a terminal phosphate group are suitable reactants in phosphoramidation reactions to conjugate with amine-containing molecules such as biotin and fluorescein derivatives, proteins, and, most importantly, peptides to enable the synthesis of POCs for therapeutic applications. Polymerase chain reactions (PCRs) to study incorporation of biotin or fluorescein-tagged DNA primers into the reaction products demonstrated that appropriate controls of nucleic acid phosphoramidation reactions incur minimum adverse effects on inherited base-pairing characteristics of nucleotides in nucleic acids. The phosphoramidation approach preserves the integrity of hybridization specificity in nucleic acids when preparing POCs. By retaining integrity of the nucleic acids, their effectiveness as therapeutic reagents for gene silencing, gene therapy, and RNA interference is ensured. The potential for POC use was demonstrated by two-step phosphoramidation reactions to successfully synthesize nucleic acid-tetraglycine conjugates. In addition, phosphoramidation reactions provided a facile approach to prepare nucleic acid-BSA conjugates with good yields. In summary, the new approach to phosphoramidation reactions offers a universal method to prepare POCs and other nucleic acid conjugates with high yields in aqueous solutions. The methods can be easily adapted to typical chemistry or biology laboratory setups which will expedite the applications of POCs for basic research and medicine.

Proteomic alteration of mitochondrial aldehyde dehydrogenase 2 in sepsis regulated by heat shock response.

The present study was designed to investigate the proteomic alteration of hepatic mitochondria during sepsis and to explore the possible effects induced by heat shock treatment. Sepsis was induced by cecal ligation and puncture in Sprague-Dawley rats. Liver mitochondrial proteins were isolated and evaluated by 2-dimensional electrophoresis with broad pH-ranged (pH 3 - 10) immobile DryStrip and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein spots were visualized with silver stain and analyzed by Bio-2D software. Results showed that around 120 dominant spots could be separated and visualized distinctly by 2-dimensional electrophoresis analysis. Among them, three spots with the same molecular weight (56.4 kd), mitochondrial protein 1 (MP1), MP2, and MP3, were significantly altered in septic specimens. When analyzed by liquid chromatography-tandem mass spectrometry, the three spots all revealed to be an identical enzyme: aldehyde dehydrogenase 2 (ALDH2, EC 1.2.1.3). During sepsis, MP1 and MP2 were downregulated, whereas MP3 was upregulated concomitantly. Interestingly, heat shock treatment could reverse this phenomenon. Phosphoprotein staining showed that the degree of phosphorylation is higher in MP1 and MP2 than that in MP3. The enzyme activity assay showed that ALDH2 activity was downregulated in nonheated septic rats of 18 h after cecal ligation and puncture operation, and preserved in heated septic rats. The results of this study suggest that posttranslation modification, highly possible the phosphorylation, in ALDH2 may play a functional role in the pathogenesis of sepsis and provide a novel protective mechanism of heat shock treatment.

Lipid peroxidation in workers exposed to aluminium, gallium, indium, arsenic, and antimony in the optoelectronic industry.

OBJECTIVE: The objective of this study was to investigate whether exposure to aluminum, gallium, indium, arsenic, and antimony induces lipid peroxidation in humans. METHODS: Whole blood and urine levels of 103 exposed electronic industry workers and 67 referents were analyzed by use of inductively coupled plasma mass spectrometry. Malondialdehyde (MDA), the product of lipid peroxidation, was determined by high-performance liquid chromatography. RESULTS: The mean plasma MDA level in the 103 workers was significantly higher than that in 67 referents. The levels of MDA in the exposed workers were correlated significantly with the levels of urinary gallium and arsenic. CONCLUSIONS: Malondialdehyde as an index of lipid peroxidation can be induced by gallium and arsenic exposure. By reducing exposure to these metals, biologic effects such as lipid peroxidation may also be diminished.

Synthesis, molecular structure and characterization of allylic derivatives of 6-amino-3-methyl-1,2,4-triazolo[3,4-f][1,2,4]-triazin-8(7H)-one.

1-Allyl- (2) and 7-allyl-6-amino-3-methyl-1,2,4-triazolo[3,4-f][1,2,4]triazin-8(7H)-one (3) were obtained via the 18-crown-6-ether catalyzed room temperature reaction of 6-amino-3-methyl-1,2,4-triazolo[3,4-f][1,2,4]triazin-8(7H)-one (1) with potassium carbonate and allyl bromide in dry acetone. The structures of these two derivatives were verified by 2D-NMR measurements, including gHSQC and gHMBC measurements. The minor compound 2 may possess aromatic character. A single crystal X-ray diffraction experiment indicated that the major compound 3 crystallizes from dimethyl sulfoxide in the monoclinic space group P2(1)/n and its molecular structure includes an attached dimethylsulfoxide molecule, resulting in the molecular formula C(10)H(16)N(6)O(2)S. Molecular structures of 3 are linked by extensive intermolecular N-H...N hydrogen bonding [graph set C(1)(1)(7)]. 1 Each molecule is attached to the dimethyl sulfoxide oxygen via N-H...O intermolecular hydrogen bonding. The structure is further stabilized by pi-pi stacking interactions.

Synthesis and molecular structure of 6-amino-3-benzylmercapto-1,2,4-triazolo[3,4-f][1,2,4]triazin-8(7H)-one.

The title compound 6-amino-3-benzylmercapto-1,2,4-triazolo[3,4-f][1,2,4]-triazin-8(7H)-one (4), molecular formula C(11)H(10)N(6)OS, was obtained by the reaction of 3-amino-2-benzyl-6-hydrazino-1,2,4-triazin-5(2H)-one (3) with carbon disulfide in a water/pyridine mixture. Compound 4 can also be synthesized by reacting 6-amino-3(2H)mercapto-1,2,4-triazolo[3,4-f][1,2,4]triazin-8(7H)-one (7) with benzyl bromide in methanolic ammonia water. The compound crystallizes in the monoclinic space group P2(1)/c with a = 7.2926(15), b = 14.456(2), c = 11.436(2) A, beta = 105.30(2) degrees , V= 1162.9(4) A(3) and Z = 4, resulting in a density Dcalc of 1.567 g/cm(3). Molecules of 4 are linked by extensive intermolecular N-H...N and N-H...O hydrogen bonding [graph set R(2)(2 )(9)]. The structure is further stabilized by pi-pi stacking interactions.

Building collapse and human deaths resulting from the Chi-Chi Earthquake in Taiwan, September 1999.

In this study, the authors attempted to determine factors associated with earthquake deaths in the great Chi-Chi Earthquake that occurred on September 21, 1999, in Taiwan. An isoseismal map was used to identify life-threatening hazards. The vertical peak ground acceleration of ground motion intensity was deemed the most appropriate index for the evaluation of building collapse and mortality. Mortality increased with the increase in earthquake intensity, and building collapse, approaching the epicenter. The greatest number of collapsed buildings and human deaths occurred between the Chelungpu Fault and the Shuantun Fault. Individuals 65 yr of age and older were the most vulnerable to the impact. The authors' findings suggest that improvements in earthquake-resistant building design and construction, as well as improved medical rescue for the elderly, could reduce the level of exposure to earthquake hazards.