[Strand separation and its effect on melting of shear-degraded DNA]

The degree of strand separation (mu) of shear-degraded phage T2 DNA on melting was investigated. The average size of fragments (n) varied in the range from 1000 to 300 base pairs. The obtained relationship between mu and 1/n was compared with the relationship between melting temperature depression (delta Tm) and 1/n. Both relationships are nonlinear. The correlation between the relationship delta Tm(1/n) and mu0,5(1/n) enables to believe that nonlinearity of the relationship delta Tm(1/n) is governed by the process of strand separation of DNA fragments on melting.