Polydispersity and chain break effects on DNA intramolecular renaturation

The influences of sample polydispersity and of internal chain breaks are introduced in the formal description of intramolecular renaturation phenomenology, enhancing the usefulness of the involved methodology. In our method, renaturation is induced not by cooling but by increasing the sodium concentration. The single-stranded size distributions for the two types of samples employed (haplotomic and diplotomically degraded) are discussed. In the case of haplotomic cleavage, the variable is the strand size in the 'segment' between consecutive nicks in either of the native DNA strands. Our equations have been obtained by considering that the arrangement of DNA sequences may be approximately taken as random. These equations provide a good description of experimental data and a reasonable value (about 1000 base-pairs) for the size of the thermalite sequence, but show low sensitivity to departures from the random arrangement of sequences.