Biological interphases partitioning

On the other hand, the presence of hydrophobic complexes is a prerequisite for partitioning and diffusion of metals into the lipid bilayer. In the following paragraphs, various types of metal complexes will be discussed, which are relevant to the interactions of metals in aquatic systems. The role of these various types of metal complexes with respect to interactions at the biological interphases will be systematically examined. 

In the following section, the role of the various types of complexes mentioned above will be discussed with regard to various mechanisms of interactions at biological interphases. It is clear that metal ions and hydrophilic complexes cannot distribute into the membrane lipid bilayer or cross it. The role of hydrophilic ligands has thus to be discussed in relation to binding of metals by biological ligands. In contrast, hydrophobic complexes may partition into the lipid bilayer of membranes (see below, Section 6). 

There is an abundant research on the interactions of HIOCs and metals with biological interphases, in which organic chemicals and metals are treated independently. However, few studies have considered the role of combinations of HIOCs with metals. There is a particular lack of mechanistic approaches. With regard to the metals, the FIAM has been very successful, but it remains to be shown under which conditions additional interactions, such as partitioning of hydrophobic complexes and uptake of specific complexes, are important for metal uptake and toxic effects. In particular, the role of hydrophobic complexes with both natural and pollutant compounds in natural waters has not yet been fully elucidated, since neither their abundance nor their behaviour at biological interphases are known in detail. 

Referring once more to the effect of the aqueous medium composition upon the relative hydrophobicity of biological solutes, the correlation relationship establish-ecj io3,u6) between the effects of the medium ionic composition on the relative hydrophobicity of serum albumins of various origin and on that of erythrocytes from the same species should be noted. The ionic strength value of the medium in the aqueous ficoll-dextran biphasic system has been used as a quantitative index of the ionic composition of the system, and the ionic composition was varied from 0.11 M phosphate buffer to 0.15 M NaCl in 0.01 M buffer at pH 7.4 116). Partition coefficients of cells in an aqueous polymeric biphasic system are determined as the ratio of a number of the cells in the phase to that of the cells present at the interphase 90). Specific features of the partition behavior of cells in aqueous biphasic systems are discussed in detail elsewhere (see, e.g., Ref. 90 91). It has been established 116) that erythrocytes of different species are distributed in the aqueous ficoll-dextran biphasic system according to the following equation ... 

Two examples of modern clean-up methods that use columns that have been prepared commercially are the Extube (Analytichem International) and the Sep-Pak (Waters). The Extube was designed to isolate drugs from a complex biological sample by the principle of liquid-liquid extraction. Samples to be analyzed, such as urine, whole blood or bile, are introduced into a disposable Extube, which is packed with an inert fibrous matrix of large surface area. When a suitable solvent is poured into the Extube, it interphases film-on-film with the sample. The compound of interest is extracted by a solvent that passes freely through the matrix, whereas impurities such as water, pigment, particulate matter and other polar components are retained by the matrix. The Extube has been used to extract and purify cortisol from plasma by liquid-liquid partition with methylene chloride [40]. The Sep-Pak... 

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