Irreversible changes in phage DNA after its protonation in solution and inside the virion detected by the transfection method

: The dependence of irreversible structural changes in phage lambda DNA on the degree of its protonation in a solution and inside the virion has been found by measuring the transfection activity of bacteriophage. The different effect of ionic strength on pH-dependence of the irreversible changes in the structure of DNA upon its protonation in a solution or in situ has been registered and explained. The insignificant shift of pH from neutral region value in 0.1 M NaCl has resulted in a damaging effect of H+ ions on compact DNA in situ as compared to the DNA in a solution. The effect of H+ ions on compact DNA in situ is mainly based on the formation of noncovalent intermolecular DNA-protein and DNA-DNA linkages.