FIGURE 7.
Semilogarithmic representation of the interaxial spacing aH as a function of the spermine salt concentration in the low DNA concentration range (lines 1b and 1c in Fig. 1). Experiments were performed with short fragments, except the four points that correspond to long λ-DNA molecules, as indicated in the figure. The dilution of the spermine-DNA sample was performed in distilled water (•), 50 mM NaCl (▴), 100 mM NaCl (▾), and 200 mM NaCl (▪). At each salt concentration, the constant spacing is indicated by a horizontal line. The curve corresponds to Eq. 4. The dilution of the four Na-λ DNA samples was performed in 10 mM TE (○), 10 mM TE + 40 mM NaCl (▵), 10 mM TE + 90 mM NaCl (∇), and 10 mM TE + 190 mM NaCl (□).