Membrane hydrophobic damage

The PAHs most common action mechanism that result in toxicity for the organisms is related with the interference in the cellular membranes function by the bond in the membrane hydrophobic sites, causing deformity and molecular perturbance, besides alterations in the enzymatic system (Tuvikene, 1995). As a consequence of these bonds, the membrane permeability is altered and the substances transport in and out the cells is damaged. Moreover, as many enzymatic systems are associated with structure of the membrane, other essential process for the cells can be damaged and the normal energy balance becomes debilitated (Knutzen, 1995). 

Because the carotenoids favour hydrophobic domains they are generally localised in the membranes and lipoproteins of animal cells. In this location they can influence the oxidation of membrane lipids and prevent the passage of free radicals from one cellular compartment to another. Thus, DNA in the nucleus is protected from intracellularly generated ROS by (at least) the nuclear membrane and from extracellular ROS by a number of membranes. Should ROS reach the nucleus, base oxidation can occur. The base most susceptible to oxidation is guanine, although all other bases can also be affected. The cell has the ability to detect damaged bases, excise them. 

These in vitro cytotoxicity studies are not indicative of in vivo toxicity but rather provide a method to classify the CDs for their potential to destabilize or disrupt cellular membranes. In fact, when whole blood is used instead of erythrocytes for the hemolysis tests, the cytotoxicity of the CDs is diminished 10-fold by the presence of hydrophobic serum components. Thus, the membrane damaging effects of the CDs are observed in vivo only under situations of high concentrations. 

The two major morphological parts in the structure of wool are cuticle and cortex. The epi-cuticle of wool fibres surrounds each cuticle, it consists of approximately one-quarter fatty acid and three-quarters protein by mass. The hydrophobic epiCLiticle acts as a barrier to dyes which enter the wool fibre between cuticle cells through the highly cross-linked cell membrane complex (CMC). Enzyme from the liquor can diffuse into the interior of the fibre and hydrolyse parts of the endocuticle and proteins in the cell membrane complex, completely damaging the fibre if not controlled. In contrast, the catalytic action of enzyme on cotton is confined to the surface and the amorphous region only. 

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