Effects of diadenosine 5',5'''-P1, P4-tetraphosphate and of adenosine 5'-triphosphate on the higher order structure of calf thymus DNA.

The effective length and the hard core radius were calculated by scaled particle theory for high molecular weight calf thymus DNA in the presence of varying concentrations of diadenosine 5',5'''-P1, P4-tetraphosphate and of adenosine 5'-triphosphate in aqueous millimolar NaCl. DNA became slightly more flexible in the presence of diadenosine 5',5'''-P1, P4-tetraphosphate at concentrations of 10(-9)-10(-7) M. DNA was denatured in the presence of 5 X 10(-5) M adenosine triphosphate.