A general theory of DNA strand break production by direct and indirect effects

A general theory of the production of strand breaks by energetic electrons and heavy charged particles has been developed. This theory is based on chemical and biochemical mechanisms and does not require adjustable parameters. In order to avoid the complexities of a cellular system, we have referenced our calculations to systems consisting of aqueous solutions of SV40 DNA containing different amounts of tris-HCl buffer. It appears from the calculations that at 500 mM tris, the strand break yields are similar to those observed in a cellular complex when normalised to account for DNA length. Furthermore, the results indicate that the indirect action is not negligible in creating strand breaks. The difference between DNA breaks with and without histones has also been analysed. (author)