Lipids, sorption

An additional study was performed on Biomer strips to evaluate lipid sorption during the first 2 weeks of exposure. Samples, prepared from 0.3-mm-thickfilm, were cut into 5.5 mm X 50 mm strips. Before exposure samples were prepared, similar to the previously mentioned study, gravimetric analysis was performed on odd days for 2 weeks. Five samples were prepared per exposure period. Preweight sample preparations were performed as in the previous study. 

Figure 1. Elastomer weight gains due to in vitro lipid sorption. Key , Pellethane Experimental Q> Pellethane 2300 series H, PolyHexene-H O, Biomer A, Polyphosphazene PNF 200 and A, Polyphosphazene PNF 200.

Figure 2. Biomer weight gains due to in vitro lipid sorption.

Polymer-derived monomeric and oligomeric species are readily extractable from Biomer LVAD bladders. Lipid sorption definitely occurs in vitro on/in various elastomers presently being used or considered for LVAD or AHD applications. Apparently, lipid sorption does occur in vivo, and may be involved in surface calcification observed on both smooth and textured... 

European J Lipid Sci Technol 103 505-550 Grim RE (1968) Clay mineralogy, 2nd edn. McGraw-Hill, New York Groisman L, Rav-Acha C, Gerstl Z, Mingelgrin U (2004) Sorption and detoxification of toxic compounds by a bifunctional organoclay. J Environ Qual 33 1930-1936... 

Historically, organic environmental pollutants were hydrophobic, often persistent, neutral compounds. As a consequence, these substances were readily sorbed by particles and soluble in lipids. In modern times, efforts have been made to make xenobiotics more hydrophilic - often by including ionisable substituents. Presumably, these functional groups would render the compound less bioaccumulative. In particular, many pesticides and pharmaceuticals contain acidic or basic functions. However, studies on the fate and effect of organic environmental pollutants focus mainly on the neutral species [1], In the past, uptake into cells and sorption to biological membranes were often assumed to be only dependent on the neutral species. More recent studies that are reviewed in this chapter show that the ionic organic species play a role both for toxic effects and sorption of compounds to membranes. 

If the adsorption sites are not localised in space (as is the case for sorption to a fluid lipid membrane), then the Langmuir equation could be transformed to the Volmer isotherm [7],... 

Figure 3.3 shows that the log /fow-log sw plot for compounds with log Kow > 5 deviates from linearity. This phenomenon is also observed for plots of log bioconcentration factor (BCF) versus log Ko (Connell, 1990). Chiou (1985) has shown that a similar deviation occurs in a triolein-water system alone, at log Ko > 5.5, as a result of solute-triolein incompatibility. Similarly, Banerjee and Baughman (1991) argued that BCFs of large molecules are smaller than expected on the basis of their hydrophobicity as a result of their disrupting effect on the structure of the lipid phase. The curvilinearity is not likely to be caused by sorption to DOC in the experimental systems (Section 3.4.), because deviations from linearity already occur at log /fow 5, whereas the effect of DOC-bo mA contaminants can only be expected at log /fow values > 7. 

Processing of the triolein alone (i.e., without analyzing the LDPE as well) is not encouraged for a number of reasons. First of all, the LDPE constitutes a significant part of the total SPMD sorption capacity, in contrast to biota, where the sorption capacity of the non-lipid phase is often considered to be negligible. Data on membrane-lipid partition coefficients (/fmc) is very limited, but the available... 

The partition coefficient Kq of an organic compound in the 1-octanol/water system is used to assess the bioaccumulation potential and the distribution pattern of drugs and pollutants. The partition coefficient of imidazole and ILs strongly depends on the hydrogen bond formed by these molecules and is less than one due to the high solubility in water. The low value of the 1-octanol/water partition coefficient is required for new substances, solvents, insecticides to avoid bioaccumulation. Kqw is an extremely important quantity because it is the basis of correlations to calculate bioaccumulation, toxicity, and sorption to soils and sediments. Computing the activity of a chemical in human, fish, or animal lipid, which is where pollutants that are hydrophobic will appear, is a difficult task. Thus, it is simpler to measure the 1-octanol/water partition coefficient. This parameter is used as the primary parameter characterizing hydrophobisity. 

The concentrations of PFAs in environments have increased sharply over time (Holmstrom et al., 2005). The sorption/accumulation and fate of PFAs differ from classical chlorinated and brominated POPs in that perfluorinated molecules have surfactant characteristics (i.e., having polar and nonpolar domains) and oleophobic properties. Thus, PFAs is likely to bind to serum protein rather than lipid in tissues (Jones et al., 2003). 

Transcellular transport Sorption promoters can be used to enhance the transcellular transport in the intestine, including bile salts and fatty acid esters. They tend to fluidize the lipid bilayer and enhance drug permeation across the membrane. 

Additives to starch exert varying effects on the kinetics of water sorption. For example, lipids do not significantly affect the content of adsorbed water. The mode of starch defatting can also influence moisture sorption by molecules of the defatting solvent occupying active centers of sorption.389 The addition of either sucrose or lipids to starch has the same effect on both branches of the hysteresis curve.386,398 Some additives, such as dimethyl sulfoxide or ammonium rhodanide, induce selectivity of the adsorption and solvation of starch 411 Sulfur dioxide accelerates water sorption regardless of the temperature.412 Pretreatment of starch with sulfur dioxide usually increases the water sorption.413 Studies on the sorption of components of water-alcohol mixtures are discussed in Section IV. 

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