Phytochemicals Perturb Membranes and Promiscuously Alter Protein Function

A wide variety of phytochemicals are consumed for their perceived health benefits. Many of these phytochemicals have been found to alter numerous cell functions, but the mechanisms underlying their biological activity tend to be poorly understood. Phenolic phytochemicals are particularly promiscuous modifiers of membrane protein function, suggesting that some of their actions may be due to a common, membrane bilayer-mediated mechanism. To test whether bilayer perturbation may underlie this diversity of actions, we examined five bioactive phenols reported to have medicinal value: capsaicin from chili peppers, curcumin from turmeric, EGCG from green tea, genistein from soybeans, and resveratrol from grapes. We find that each of these widely consumed phytochemicals alters lipid bilayer properties and the function of diverse membrane proteins. Molecular dynamics simulations show that these phytochemicals modify bilayer properties by localizing to the bilayer/solution interface. Bilayer-modifying propensity was verified using a gramicidin-based assay, and indiscriminate modulation of membrane protein function was demonstrated using four proteins: membrane-anchored metalloproteases, mechanosensitive ion channels, and voltage-dependent potassium and sodium channels. Each protein exhibited similar responses to multiple phytochemicals, consistent with a common, bilayer-mediated mechanism. Our results suggest that many effects of amphiphilic phytochemicals are due to cell membrane perturbations, rather than specific protein binding

Comparison of the adsorption characteristics of azo-reactive dyes on mezoporous minerals

Sepiolite and zeolite, highly porous minerals, are becoming widely used as alternative materials in areas where sorptive, catalytic and rheological applications are required. High ion exchange capacity and high surface areas and more importantly their relatively cheap prices make them attractive adsorbents. In this study, the adsorption mechanism of three reactive azo dyes (Reactive Black 5, Red 239 and Yellow 176) by two natural mezoporous minerals has been examined in order to identify the ability of these minerals to remove coloured textile dyes from wastewaters. For this purpose, a series of batch adsorption tests were carried out as a function of solids concentration, time and dye concentration using natural and modified sepiolites and zeolites. The adsorption results indicate that both natural sepiolite and zeolite have limited adsorption capacities of the reactive dyes but are substantially improved upon modifying their surfaces with quaternary amines. The mechanism of adsorption process is elucidated on the basis of experimental data. (C) 2003 Elsevier Ltd. All rights reserved

Adsorption of negatively charged azo dyes onto surfactant-modified sepiolite

The adsorption of reactive dyes on sepiolite has been investigated in a series of batch adsorption experiments. Three reactive dyes (Everzol Black B, Everzol Red 3BS, Everzol Yellow 3RS H/C) were used in bottle adsorption studies. While no significant adsorption capacity was obtained for natural sepiolite, high-adsorptive capacities were observed upon using sepiolite modified with quaternary amines. The electrokinetic measurements along with calculations using the cross-sectional area reveal that the quaternary amines adsorb close to bilayer coverage. A mechanism involving electrostatic attraction of the anionic groups of dye molecules onto oppositely charged amine-modified sepiolite surface is proposed to be responsible for the uptake of dyes. The adsorption data were fitted to the Langmuir isotherm. It is found that the modified sepiolite yields adsorption capacities (q(e)) of 169, 120, and 108 mg/g for Yellow, Black, and Red, respectively. These results are comparable to the adsorption capacity of the same dyes onto activated carbon

Color removal of reactive dyes from water by clinoptilolite

The adsorption of reactive dyes on Gordes (Turkey) clinoptilolite was investigated by a series of batch and column adsorption experiments. Three reactive dyes (Everzol Black, Everzol Red. Everzol Yellow) were used in laboratory studies. Synthetic wastewaters were used and the ability of natural zeolite (clinoptilolite) and their modified form were examined. The adsorption results, in batch and column reactor, indicate that natural zeolite have limited adsorption capacities of the reactive dyes but are substantially improved upon modifying their surfaces with quaternary amines (HTAB). The degree of hydrophilicity is found to play an important role in the uptake of reactive dyes

Clay mineral batch process for color removal of textile wastewaters

Textile industry effluents exhibit large amounts of dye chemicals, which create severe water pollution. It is therefore important to reduce the dye concentration in the wastewater before discharging into the environment. In this study, the ability of sepiolite to uptake different reactive dyes is investigated. The dyes used in the experiments are Everzol Black B, Everzol Yellow 3RS H/C, and Everzol Red 3BS. A number of parameters on adsorption has been investigated in order to establish the adsorption pattern of sepiolite. The effect of conditioning time, solid/liquid ratio, pH, temperature, and dye concentrations on adsorption are studied. Adsorption isotherms for different reactive dyes have been obtained using both natural and modified sepiolites. The maximum capacity of natural sepiolite for the reactive dyes occurs at around 0.1-1 mg/g. Therefore, the natural sepiolite appears to have a little capacity for reactive dyes. The zeta potential profiles of natural and modified sepiolites against pH are also examined. The modified sepiolite exhibited ten times higher performance than the natural sepiolite