60
all titrations are presented in Tables 2 through 17. Note
that volume corrections for the addition of DNA solution
to the sample were made in all cases.
The equilibrium association constants for the
surface and intercalative modes of binding were calculated
for each point in the absorptiometric titrations of the
small molecules with DNA, using the relationships developed
by A.C. Capomacchia and S.G. Schulman (85).
(2-15)
Ks = [BHP]/[BH]([Pt/3]-[BHP])
and
2
(2-16)
KI = [BHP]/[BH]([Pfc/2]2[BHP])
where Kg and are the apparent association constants
for the surface and intercalative modes, respectively, and
P is the total molar DNA phosphate concentration. The
equations for the binding of 7-aminoquinolinium to DNA
are the same except [AHP] and [AH] are substituted for
[BHP] and [BH] respectively. The extended Debye-Hiickel equation
(1-28) was used to calculate activity coefficients at the
various ionic strengths, for charged species involved in
the association equilibrium.
Apparent association constants were corrected for
deviations of molar concentration from activity, by
(2-17)