The effect of magnetic fields in chemistry and biology

This thesis is concerned with the effect of static and oscillatory magnetic fields on the yield of radical recombination reactions and the proposal that such effects may constitute a possible mechanism for the interaction of environmental electromagnetic fields with biological systems. A brief overview of research pertaining to the biological effects of environmental electromagnetic fields is presented. Next, the concept of the radical pair is introduced and the theory of its behaviour in solution is examined in order to illustrate the mechanism by which magnetic fields can affect its probability of separation. Three different experimental systems involving the attack of free-radicals on DNA are presented. The extent of DNA damage is assayed in the presence and absence of a static magnetic field. These systems involve the killing of yeast cells as observed by the growth of subsequent colonies, direct observation of strand breaks to DNA, in vitro, by gel electrophoresis and the direct observation of intra- nuclear DNA damage by microgel analysis. In all systems, magnetic field effects are observed but are difficult to reproduce consistently. The design of novel apparatus for the observation of resonant radiofrequency effects is described. The application of a 30-40 MHz oscillating magnetic field is found to alter the yield of exciplex fluorescence in the photoreaction of anthracene-d10 and 1,3-dicyanobenzene. The effect is interpreted in terms of a change in the efficiency of singlet andleftrightarrow; triplet interconversion in the {anthracene cation - DCB anion} radical pair when the oscillating field is in resonance with hyperfine splittings in the DCB anion radical.