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A quaternary ammonium salt (A), a bisquaternary (FB), and an amine oxide (B) were tested for biodegradability using bacterial strains isolated from a municipal waste-water treatment plant Adsorption of the compounds by the cells was distinguished from actual biodegradation. The bisquaternary hard detergent FB was of lower affinity to the bacterial cells in comparison to soft compound A, where adsorption is accompanied by degradation. A soft surfactant, amine oxide (B) is also degraded without marked adsorption by cells. Adsorption of the compouds by the cells is also lower in mineral biodegradation medius where cell membranes are stabilised by ions.
It has been shown that the time course of echinocyte to discocyte transformation caused by exogenous phospholipids is an accurate measure of the flip rate of the phospholipids in the lipid bilayer [1,2]. In order to explore whether shape changes in erythrocytes are indicative of flip rates of water- soluble amphiphiles, the time course of shape changes caused by a large number of amphiphiles was studied. In case of amphiphiles inducing echinocyte to discocyte or discocyte to stomatocyte transformation it is proposed that the time course of shape transformation may be indicative of the flip rate of the amphiphiles. The relevance of using shape changes in erythrocytes as a tool to estimate flip rates of amphiphiles is discussed.
The change of biological activity of amphiphilic biocides following the change of their hydrophobic parts (the cut-off effect) is discussed. The mechanism of the interaction (between such amphiphiles and model and biological membranes is proposed that explains the cut-off phenomenon. It is proposed, on the basis of experimental studies and theoretical calculations, that the diminished biological activity of amphiphilic compounds upon elongation of thier hydrophobic part can be the result of the appearance of interdigitated structures in the lipid bilayers. On the other hand, weak hydrophobic interactions between amphiphilic compounds of short hydrophobic chins and lipid molecules of model membranes are responsible for the poor biological activity of these compounds.
On the basis of Gortel & Grendel (J. Exp. Med., 1925, 41, 439-494) discovery, the importance of the lipid bilayer as an integral and indispensible component of the cell membrane is discussed. In particular, attention focuses on the interaction between membranes and amphiphilic substances. The effect on membranes of quaternary ammonium salts, both in the form of pesticides and oxidants as well as organic compounds of tin and lead are discussed in greater detail.
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