The cis‐Diammineplatinum(II) Complex of Curcumin: A Dual Action DNA Crosslinking and Photochemotherapeutic Agent

[Pt(cur)(NH₃)₂](NO₃) ( 1 ), a curcumin‐bound cis‐diammineplatinum(II) complex, nicknamed Platicur, as a novel photoactivated chemotherapeutic agent releases photoactive curcumin and an active platinum(II) species upon irradiation with visible light. The hydrolytic instability of free curcumin reduces upon binding to platinum(II). Interactions of 1 with 5′‐GMP and ct‐DNA indicated formation of platinum‐bound DNA adducts upon exposure to visible light (λ=400–700 nm). It showed apoptotic photocytotoxicity in cancer cells (IC₅₀≈15 μM ), thus forming ^?OH, while remaining passive in the darkness (IC₅₀>200 μM ). A comet assay and platinum estimation suggest Pt–DNA crosslink formation. The fluorescence microscopic images showed cytosolic localization of curcumin, thus implying possibility of dual action as a chemo‐ and phototherapeutic agent.     

Enhanced preconcentration of selected chlorofluorocarbons on multiwalled carbon nanotubes with polar functionalities

Chromatographic monitoring of chlorofluorocarbons in air requires the preconcentration of these highly volatile species. In this paper, we present functionalized multiwalled carbon nanotubes as effective sorbents for a microtrap designed for chlorofluorocarbons preconcentration. Among the commercial carbons and carbon nanotubes studied, functionalization via carboxylation and propyl amine was most effective for dichlorofluoromethane and trichlorofluoromethane (Freon 11), which were selected as representative chlorofluorocarbons. The results show that carbon nanotubes functionalized with a polar groups led to as much as a 300% increase in breakthrough volume and the desorption bandwidth was reduced by 2.5 times.     

Computational study of the mechanism and selectivity of ruthenium-catalyzed hydroamidations of terminal alkynes

Density functional theory calculations were performed to elucidate the mechanism of the ruthenium-catalyzed hydroamidation of terminal alkynes, a powerful and sustainable method for the stereoselective synthesis of enamides. The results provide an explanation for the puzzling experimental finding that with tri-n-butylphosphine (P(Bu)₃) as the ligand, the E-configured enamides are obtained, whereas the stereoselectivity is inverted in favor of the Z-configured enamides with (dicyclohexylphosphino)methane (dcypm) ligands. Using the addition of pyrrolidinone to 1-hexyne as a model reaction, various pathways were investigated, among which a catalytic cycle turned out to be most advantageous for both ligand systems that consists of: (a) oxidative addition, (b) alkyne coordination, (c) alkyne insertion (d) vinyl-vinylidene rearrangement, (e) nucleophilic transfer and finally (f) reductive elimination. The stereoselectivity of the reaction is decided in the nucleophilic transfer step. For the P(ⁿBu)₃ ligand, the butyl moiety is oriented anti to the incoming 2-pyrolidinyl unit during the nucleophilic transfer step, whereas for the dcypm ligand, steric repulsion between the butyl and cyclohexyl groups turns it into a syn orientation. Overall, the formation of E-configured product is favorable by 4.8 kcal mol^–1 (Δ^‡ GSDL) for the catalytic cycle computed with P(Bu)₃ as ancillary ligand, whereas for the catalytic cycle computed with dcypm ligands, the Z-product is favored by 7.0 kcal mol^–1 (Δ^‡ GSDL). These calculations are in excellent agreement with experimental findings.     

Augmentation of heat transfer in a bubble agitated vertical rectangular channel

This paper presents the results of an experimental study of convective heat transfer between three parallel vertical plates symmetrically spaced with and without bubble agitation to ascertain the degree of augmentation of the heat transfer coefficients due to agitation. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical rectangular channels of dimensions 20 cm × 3.5 cm × 35 cm (length W, gap L, height H) each. At the bottom of the hot and cold plates air spargers were fitted. Water/ethylene glycol (100%) was used to fill the channels. The superficial gas velocity ranged from 0.0016 to 0.01 m/s. Top, bottom and sides of the channels were open to the water/ethylene glycol in the chamber which is the novel aspect of this study. Experimental data have been correlated as under: Natural convective heat transfer: Nu = 0.60 Gr ^0.29, r = 0.96, σ = 0.186, 1.17 E6 < Gr < 1.48 E7; Bubble agitated heat transfer: St = 0.11(ReFrPr ²)^−0.23, r = 0.82, σ = 0.002, 1.20 E−2 < (ReFrPr ²) < 1.36 E2.     

CFD modeling of catalyst pellet for oxidative coupling of methane: Heat transfer and reaction

This study deals with the phenomena occuring at single-pellet catalyst scale for the oxidative coupling of methane where heat transfer plays an important role. Computational fluid dynamics (CFD) is used for obtaining detailed rate and temperature profiles through the porous catalytic pellet where reaction and diffusion compete. Intra-particle temperature and concentration gradients were taken into account by solving heat transfer coupled with continuity equations in the catalyst pellet. In heat transfer, the energy term due to highly exothermic reaction was considered. Two external programs were successfully implemented into the CFD-code as kinetic and heat of reaction terms. Simulation results showed that reaction was favored at the beginning for the pellet, followed by diffusion predomination. The results of CFD simulation indicate that temperature variation within the catalyst pellet is <2 K due to exothermic oxidation. The results showed further that exothermic oxidation reactions occurred prior to endothermic coupling reaction in the pellet.     

Potassium Ferrate Supported on Montmorillonite K-10: A Mild and Efficient Reagent for Oxidative Deprotection of Acetals and Ketals

Summary.  A variety of acetals and ketals were oxidatively deprotected to their parent compounds using potassium ferrate(VI) supported on montmorillonite K-10 under non-aqueous conditions. Received January 23, 2001. Accepted (revised) March 14, 2001     

Berberine as a Potential Anticancer Agent: A Comprehensive Review

Berberine (BBR), a potential bioactive agent, has remarkable health benefits. A substantial amount of research has been conducted to date to establish the anticancer potential of BBR. The present review consolidates salient information concerning the promising anticancer activity of this compound. The therapeutic efficacy of BBR has been reported in several studies regarding colon, breast, pancreatic, liver, oral, bone, cutaneous, prostate, intestine, and thyroid cancers. BBR prevents cancer cell proliferation by inducing apoptosis and controlling the cell cycle as well as autophagy. BBR also hinders tumor cell invasion and metastasis by down-regulating metastasis-related proteins. Moreover, BBR is also beneficial in the early stages of cancer development by lowering epithelial–mesenchymal transition protein expression. Despite its significance as a potentially promising drug candidate, there are currently no pure berberine preparations approved to treat specific ailments. Hence, this review highlights our current comprehensive knowledge of sources, extraction methods, pharmacokinetic, and pharmacodynamic profiles of berberine, as well as the proposed mechanisms of action associated with its anticancer potential. The information presented here will help provide a baseline for researchers, scientists, and drug developers regarding the use of berberine as a promising candidate in treating different types of cancers.     

Large eddy simulation in a turbulent channel flow using exit boundary conditions

The influence of the exit boundary conditions on the vanishing first derivative of the velocity components and constant pressure on the large eddy simulation of the fully developed turbulent channel flow has been investigated for equidistant and stretched grids at the channel exit. Results show that the chosen exit boundary conditions introduce some small disturbances that are mostly damped by the grid stretching. The difference of rms values between the fully developed turbulent channel flow with periodicity conditions and the fully developed channel flow using inlet and the exit boundary conditions is less than 10% for the equidistant grids and less than 5% for the stretched grids. The chosen boundary conditions are of interest because they may be used in complex problems with back flow at the exit. Copyright © 1999 John Wiley & Sons, Ltd.