Structural investigation into the threading intercalation of a chiral dinuclear ruthenium(II) polypyridyl complex through a B-DNA oligonucleotide

Herein we report the separation of the three stereoisomers of the DNA light-switch compound [{Ru(bpy)2}2(tpphz)]4+ (tpphz = tetrapyrido[3,2-a:2',3'-c:3″,2″-h:2‴,3‴-j]phenazine) by column chromatography and the characterization of each stereoisomer by X-ray crystallography. The interaction of these compounds with a DNA octanucleotide d(GCATATCG).d(CGATATGC) has been studied using NMR techniques. Selective deuteration of the bipyridyl rings was needed to provide sufficient spectral resolution to characterize structures. NMR-derived structures for these complexes show a threading intercalation binding mode with slow and chirality-dependent rates. This represents the first solution structure of an intercalated bis-ruthenium ligand. Intriguingly, we find that the binding site selectivity is dependent on the nature of the stereoisomer employed, with Λ RuII centers showing a better intercalation fit

Eugenol como anestésico para a tilápia-do-nilo Eugenol as an anesthetic for Nile tilapia

O objetivo deste trabalho foi avaliar o eugenol como anestésico para a tilápia-do-nilo. Para a concentração ideal, foram avaliados seis tratamentos (50, 75, 100, 150, 200 e 250 mg L-1), com dez peixes por tratamento, anestesiados individualmente, acompanhados durante a indução e recuperação. A toxicidade foi estimada pela submissão de 210 peixes a 7 concentrações de eugenol (50, 75, 100, 150, 200, 250, 300 mg L-1), durante 600 s e, para a margem de segurança, 120 peixes foram submetidos a 75 mg L-1 durante cinco intervalos de tempo (600, 1.200, 1.800 e 2.400 s). As concentrações eficientes foram 50 e 75 mg L-1. Os valores de toxicidade letal (CL), aos 600 s, foram: CL01, 81,97 mg L-1; CL50, 184,26 mg L-1; e CL99, 286,55 mg L-1; e os tempos de concentrações letais (TCL) foram: TCL01, 566,97 s; TCL50, 1.611,66 s; e TCL99, 2.656,34 s. Concluiu-se que 75 mg L-1 são suficientes para a anestesia profunda de curta duração, com margem de segurança de 484,27 s, e 50 mg L-1 para longos períodos (600 s). A maior concentração terapêutica do eugenol custa R$0,065 por litro de água. A eutanásia pode ser realizada com 286,55 mg L-1 durante 600 s.<br>The objective of this work was to evaluate eugenol as anesthetic for Nile tilápia. For the best concentration of the anaesthetic, six treatments (50, 75, 100, 150, 200, and 250 mg L-1) were evaluated, with ten fishes per treatment, anesthetised individually and monitored during the induction and recovery. Toxicity was estimated in 210 fish submitted to seven eugenol concentrations (50, 75, 100, 150, 200, 250, and 300 mg L-1) for 600 s; and for safety margin, 120 fish were submitted to 75 mg L-1 for five time intervals (600, 1,200, 1,800, and 2,400 s). The effective concentrations were 50 and 75 mg L-1. Lethal concentration (LC) values for 600 s were: LC01 81.97 mg L-1, LC50 184.26 mg L-1, and LC99 286.55 mg L-1. Times of lethal concentration (TLC) were TLC01 566.97 s, TLC50 1,611.66 s, and TLC99 2,656.34 s. For fast deep anesthesia, 75 mg L-1 of eugenol is recommended, with a safety margin of 484,27 s; for long period anesthesia (600 s) 50 mg L-1 were recommended. The higher therapeutic concentration costs R$ 0.065 per liter. Eugenol was effective for euthanasia at 286.55 mg L-1 for 600 s

Modeling of the Effects of Surface-Active Elements on Flow Patterns and Weld Penetration

A mathematical model was developed to calculate the transient temperature and velocity distributions in a stationary gas tungsten arc (GTA) weld pool of 304 stainless steels with different sulfur concentrations. A parametric study showed that, depending upon the sulfur concentration, one, two, or three vortexes may be found in the weld pool. These vortexes are caused by the interaction between the electromagnetic force and surface tension, which is a function of temperature and sulfur concentration, and have a significant effect on weld penetration. For given welding conditions, a minimum threshold sulfur concentration is required to create a single, clockwise vortex for deep penetration. When two metals with different sulfur concentrations are welded together, the weld-pool shape is skewed toward the metal with a lower sulfur content. Detailed physical insights on complicated fluid-flow phenomena and the resulting weld-pool penetration were obtained, based on the surface tension-temperature-sulfur concentration relationships