Metal membrane damage

Kohen, R. and M. Chevion. 1988. Cytoplasmic membrane is the target organelle for transition metal mediated damage induced by paraquat in Escherichia coli. Biochemistry 27 2597-2603. 

A variety of responses can be initiated by the direct interaction of metals with cellular components. Membrane damage and enzyme inhibition are examples of such a metal effect. Above a certain threshold concentration of metals in the cell, its physiological state is irreversibly changed (Van Assche et al., 1988). This response is reflected by an increase in capacity (activity under non-limiting substrate and coenzyme concentrations) of certain enzymes. This increase in capacity is generally called enzyme induction. These secondary, indirect effects of metals are considered to play an important role in the stress metabolism induced by toxic metal concentrations. 

Anthracydines have several modes of action leading to anticancer activity. They intercalate between base pairs in DNA, interfering with nucleic acid synthesis. Anthracydines also inhibit DNA topoisomerases I and II, which leads to DNA double-strand breaks. In addition, doxorubicin and daunorubicin may form complexes with metals such as iron. Although these metal-anthracycline complexes result in oxygen free radical formation, which may contribute to antitumor activity, membrane damage incurred from the free radicals is thought to be the mechanism responsible for... 

Antioxidants. Excessive concentrations of ROS can have serious effects on membranes, nucleic acid bases and proteins (Section 3.1.3). If uncontrolled, mutations and membrane damage could lead to cell death. To minimize damage, defensive control systems exist. Besides enzymes, there are hydrophilic- and lipophilic-soluble molecules called antioxidants , scavenging free radicals to prevent destruction of cellular biomolecules crucial for cell viability. Non-enzymatic biological antioxidants include tocopherols, carotenoids, qui-nones, bilirubin, steroids, ascorbate, uric acid, GSH, cysteine and metal-binding proteins, such as ferritin (Krinsky, 1992). 

Prediction of Membrane Damage by Nano Metal Oxides... 

C03O4, Ce02, AI2O3) [45]. These data were used to develop computational models. The experimental results on this endpoint related to four doses (50, 100, 150, and 200 pg/mL) and seven exposure time (from 1 to 7 h) for aU 24 nano metal-oxides were examined. Figure 12.9 contains an example of the representation for (i) nano metal-oxide and (ii) conditions of its impact upon cell membrane. The data set contains the numerical values of cell membrane damage which are characterized by dispersion <10 % [46]. 

QFAR for Cellular Membrane Damage (CMD) by Metal Oxide Nanoparticles... 

Table 12.18 The model for split 1 (i) representation of the nano metal-oxides (ii) distribution into the sub-training, calibration and validation sets (iii) the numerical data on the DCW(1,10) and (iv) numerical data for cell membrane damage (CMD) [1]...

Each type of cell has its own requirements. Diaphragm cells are perhaps the most forgiving of impurities. While mercury cells can tolerate a higher total concentration because of their lesser sensitivity to the major impurities, they are susceptible to damage by small quantities of certain heavy metals. Membrane cells have the most exacting brine specification and are distinguished front the others by their very low hardness specification. 

Chlorine is desirable as a bulk pretreatment biocide for inlet water, but its subsequent removal upstream of the membrane is absolutely necessary ana difficult. NaHSO,3 is a common additive to dechlorinate before membranes. It is customarily added at 3-5 mg/1, an excess over the stoichiometric requirement. NH3 is sometimes added to convert the chlorine to chloramine, a much less damaging biocide. Heavy metals present in seawater seem to amplify the damaging effects of chlorine and other oxidants. 

Ceramic or carbon-brick linings are frequently used as facing linings over plastic or membrane linings when surface temperatures exceed those which can be handled by the unprotected materials or when the membrane must be protec ted from mechanical damage. This type of construction permits processing of materials that are too corrosive to be handled in low-cost metal constructions. 

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