Exposure to various chemicals, either due to occupation or lifestyle, is considered to be a major contributing factor to tumour formation in man (Higginson, 1969; Doll & Peto, 1981). An important and prevalent class of potent carcinogenic compounds present in the environment is polycyclic aromatic hydrocarbons (PAHs), which are found in various petroleum and combustion products derived from heat and power generation and motor vehicle exhausts (Baum, 1978). Furthermore, since PAHs are generally formed by pyrolysis of organic matters such as tobacco smoking and certain procedures of food preparation, the PAH exposure to humans is extensive

In all contemporary models of enzyme catalysis, the functional activity of enzymes is directly associated with the dynamic properties of proteins (see Blumenfeld, 1977; Chernavaskaya & Chernavskii, 1977; Volkenstein, 1975; Austin et al. 1975; Shaitan & Rubin, 1985; Ansari et al. 1985). This has recently led to a much greater interest in the dynamical properties of proteins.