Toxicology of Industrial Compounds

2. Induction of conformational changes in the tertiary or secondary
structure of the enzyme protein.
3. In the case of membrane-bound enzymes, separation of the enzyme
protein from essential membrane lipids.
4. Binding at active sites of the enzyme.
While the effect of cationic surfactants on membranes is comparable to
that of anionic surfactants, many proteins are obviously more resistant
towards the denaturing activity of .cationic surfactants (Nozaki et al.,
1974). Binding of tetradecyl trimethyl ammonium chloride onto bovine
serum albumin and other proteins is comparable to that of sodium dodecyl
sulphate. However, the cooperative binding with subsequent denaturation
requires a ten-fold higher concentration of cationic surfactant. The
saturation of the surfactant/protein complex is prevented by the competing
formation of surfactant micelles. Contrary to the irreversibly denaturing
effect of sodium dodecyl sulphate, the effect of some cationic surfactants on
proteins is reversible (Nakaya et al., 1971).
Local effects
Skin compatibility
W.STERZEL 343
The damaging effects of surfactants on skin manifest themselves in dryness,
roughness and scaling. In addition, symptoms of inflammation (reddening,
swelling) can develop, which can result, in severe cases, in complete
destruction of the tissue. All these symptoms are a result of the described
biochemical properties of surfactants. The skin is defatted by the more or
less pronounced property of the surfactants to emulsify lipids and thus
partially or completely removing the surface film of lipids. This leads to a
disturbance of the barrier function of the skin resulting in increased
permeability for chemical substances and a loss of water. Anionic
surfactants can cause swelling of the skin. As a result, they facilitate the
transport of substances to lower layers where inflammation reactions can be
induced (Scholz, 1967). The reaction of surfactants with proteins dissolves
proteins out of the skin and leads to their denaturation. These changes in
the matrix material have an effect on the resistance of the skin (Götte,
1967) and, along with degreasing and drying, are an additional cause of an
increase in skin roughness (Imokawa, 1975).
The majority of the knowledge about skin compatibility of surfactants
originates from studies with experimental animals, preferably rabbits.
Furthermore, it is possible to evaluate new substances directly on human
skin after careful exclusion of unreasonable risks. A critical overview of
different test methods is given by Kästner (1980). In this context, the