Synthetic dye--inorganic salt hybrid colorants for application in thermoplastics.

Common synthetic dyes, e.g., Weak Acid Pink Red B (APRB, C.I. 18073), Mordant Blue 9 (MB, C.I.14855) and Acid Brilliant Blue 6B (ABB6B, C.I. 42660), can be removed from water by in situ hybridization with CaCO(3), BaSO(4) and Ca(3)(PO(4))(2) and the resulting hybrids thus prepared used as plastic colorants. All the hybrids can be processed into polypropylene (PP) at 200 °C with good color intensity, color brightness and homogeneous dispersion. The BaSO(4)-MB hybrid exhibits better migration resistance to acid and alkali, and stronger covering power than the BaSO(4)-MB mixture. The thermal stability and UV resistance of the Ca(3)(PO(4))(2)-ABB6B hybrid are better than those of the Ca(3)(PO(4))(2)-ABB6B mixture. The crystallinity of PP is enhanced by incorporation of these hybrids and the use of these hybrids as colorants in PP instead of the dyes alone is determined to be feasible.

Binding of Sudan II and IV to lecithin liposomes and E. coli membranes: insights into the toxicity of hydrophobic azo dyes.

BACKGROUND: Sudan red compounds are hydrophobic azo dyes, still used as food additives in some countries. However, they have been shown to be unsafe, causing tumors in the liver and urinary bladder in rats. They have been classified as category 3 human carcinogens by the International Agency for Research on Cancer. A number of hypotheses that could explain the mechanism of carcinogenesis have been proposed for dyes similar to the Sudan red compounds. Traditionally, investigations of the membrane toxicity of organic substances have focused on hydrocarbons, e.g. polycyclic aromatic hydrocarbons (PAHs), and DDT. In contrast to hydrocarbons, Sudan red compounds contain azo and hydroxy groups, which can form hydrogen bonds with the polar head groups of membrane phospholipids. Thus, entry may be impeded. They could have different toxicities from other lipophilic hydrocarbons. The available data show that because these compounds are lipophilic, interactions with hydrophobic parts of the cell are important for their toxicity. Lipophilic compounds accumulate in the membrane, causing expansion of the membrane surface area, inhibition of primary ion pumps and increased proton permeability. RESULTS: This work investigated the interactions of the amphiphilic compounds Sudan II and IV with lecithin liposomes and live Escherichia coli (E. coli). Sudan II and IV binding to lecithin liposomes and live E. coli corresponds to the Langmuir adsorption isotherm. In the Sudan red compounds--lecithin liposome solutions, the binding ratio of Sudan II to lecithin is 1/31 and that of Sudan IV to 1/314. The binding constant of the Sudan II-lecithin complex is 1.75 x 104 and that of the Sudan IV-lecithin complex 2.92 x 105. Besides, the influences of pH, electrolyte and temperature were investigated and analyzed quantitatively. In the Sudan red compounds--E.coli mixture, the binding ratios of Sudan II and Sudan IV to E.coli membrane phospholipid are 1/29 and 1/114. The binding constants of the Sudan II--and Sudan IV- E.coli membrane phospholipid complexes are 1.86 x 104 and 6.02 x 104. Over 60% of Sudan II and 75% of Sudan IV penetrated into E.coli, in which 90% of them remained in the E.coli membrane. CONCLUSION: Experiments of Sudan II and IV binding to lecithin liposomes and live E. coli indicates that amphiphilic compounds may be sequestered in the lecithin liposomes and membrane phospholipid bilayer according to the Langmuir adsorption law. Penetration into the cytosol was impeded and inhibited for Sudan red compounds. It is possible for such compounds themselves (excluding their metabolites and by-products)not result directly in terminal toxicity. Therefore, membrane toxicity could be manifested as membrane blocking and membrane expansion. The method established here may be useful for evaluating the interaction of toxins with membranes.

Modeling and mechanism of the adsorption of copper ion onto natural bamboo sawdust.

The sorption of copper ions onto natural bamboo sawdust with cellulose-lignin polymeric structure strongly depends on pH. The adsorption capacity for copper ions increases as increasing pH and copper loadings. The fitting of copper pH boundary curve by NEM surface complexation models shows that: three-sites model including the ion exchange reaction of permanent charge fits better than two-sites model. The incorporation of the hydrated ion reaction gives better fitting results. XAFS study shows that: copper ions mainly form inner complexation with sawdust, but there is no obvious evidence on the complexation of carboxylic acid groups with copper ions. EXAFS fitting result shows that: as pH rises, the spatial configuration of copper ions shifts from tetrahedron to octahedron. Meanwhile the increase in the coordination number indicates that hydrated copper ions participate in the adsorption. Both XANES and EXFAS spectrum offer a similar explanation for copper adsorption in the range of experimental and fitting errors.

Transmembrane transport of microcystin to Danio rerio zygotes: insights into the developmental toxicity of environmental contaminants.

Microcystins (MCs) produced by cyanobacteria and their continuing "blooms" are a worldwide problem owing to the toxicity of microcystin-LR (MC-LR) to plants and animals. In the present study, we investigated membrane transport of MC-LR and its toxic effects on zebrafish embryos using fragmentation of embryos, scanning electron microscope (SEM), fluorescence microscopy, and toxic exposure tests. At a concentration < 0.04 mmol/l, MC-LR was predominantly adsorbed on outer membrane surface of embryos according to Langmuir isotherm. The absorption characteristics of MC-LR within the range from 0.05 to 0.4 mmol/l conformed to Freundlich isotherm model. At concentrations > 0.50 mmol/l MC-LR directly entered the cytoplasm via partition. Thinning and disruption of membranes was confirmed using SEM and fluorescence morphological observations. Exposure to different concentrations of MC-LR resulted in differences in membrane transport and toxicity characteristics. At low concentrations, more than 75% of the adsorbed MC-LR accumulated on the outer membrane surface and resulted in axial malformation, tail curving, and tail twisting. Increasing the concentration of MC-LR to between 0.05 and 0.4 mmol/l improved membrane transport and it was evident in cytoplasm of embryos, resulting in serious pericardial edema, hatching gland edema, hemagglutination, hemorrhage, and vacuolization. At > 0.50 mmol/l, more than 70% of the adsorbed MC-LR entered the cytoplasm and this was lethal to the embryos. The current research outlines a new method and mechanism for the transmembrane transport of large molecular weight organic compounds and could be important for studies concerning molecular toxicology.

Comparative transmembrane transports of four typical lipophilic organic chemicals.

Transmembrane transports of four kinds of lipophilic organic chemicals (LOCs) on suspending multilamellar liposomes (SML) and Escherichia coli (E. coli) were investigated, where both anthracene and phenanthrene were accorded to the lipid-water partition law and Sudan I and III to the Langmuir isothermal adsorption. Less than half of phenanthrene is transported into E. coli, where more than 60% are located in the cytoplasm. About 60% of anthracene entered the E. coli where only 10% was released into the cytoplasm. The partition coefficients of phenanthrene and anthracene partitioning from the extracellular liquid into membrane are 502 and 1190L/kg but their inverse partition coefficients are only 0.180 and 0.018kg/L. Over 60% of Sudan I and less than 40% of Sudan III accumulated on E. coli where most of them remained on the membrane. The transmembrane impedance effect (TMIE) is proposed for evaluating the cell-transport of polar LOCs.