“…Over the last two decades much attention has been paid (Eichhorn and Shin, 1968;Granot and Kearns, 1982;Rhee and Ware, 1983;Braunlin et al, 1989;Langlais et al, 1990;Duguid et al, 1995;Duguid and Bloomfield, 1996;Labarbe et al, 1996;Li et al, 1997) to the investigation of divalent metal cations binding to DNA, in the presence or absence of monovalent counterions, because of the importance of this problem from both a biological (Granot and Kearns, 1982;Manzini et al, 1990;Labarbe et al, 1996) and theoretical perspective (Manning, 1977(Manning, , 1978(Manning, , 1981. Our focus, in the general area of interaction of divalent metal cations with DNA in aqueous solution, is on understanding the nature of counterion binding to polyelectrolyte DNA.…”