Figure 1.
Chemical structure of polyamines.
Figure 2.
ITC profiles for the titration of polyamines with DNAs.
Titration of spermine with (A) CP DNA (B) EC DNA (C) ML DNA and spermidine with (D) CP DNA (E) EC DNA (F) ML DNA at 293.15 K. The top panels represent the raw data for the sequential injection of polyamines into a solution of DNA and the bottom panels show the integrated heat data after correction of heat of dilution against molar ratio of DNA/[polyamine]. The data points were fitted to one site model and the solid line represent the best fit data.
Table 1.
ITC derived thermodynamic parameters for the binding of polyamines to CP DNAa.
Table 2.
ITC derived thermodynamic parameters for the binding of polyamines to EC DNAa.
Table 3.
ITC derived thermodynamic parameters for the binding of polyamines to MLDNAa.
Figure 3.
Plot of variation of enthalpy of binding (ΔHO) with temperature.
Plots for the binding of (A) spermine with CP DNA (▪), EC DNA (•), ML DNA (▴), (B) spermidine with CP DNA (□), EC DNA (○), ML DNA (▵), (C) putrescine with CP DNA (▪), EC DNA (•), ML DNA (▴) and (D) cadaverine with CP DNA (□), EC DNA (○), ML DNA (▵).
Figure 4.
Plots of variationof thermodynamic parameters with entropy contribution.
Plot of ΔGO and ΔHO versus TΔSO for the binding of (A) spermine with CP DNA (▪,•), EC DNA (▴,▾), ML DNA (♦,◂) (B) Plot of ΔGO and ΔHO versus TΔSO of spermidine with CP DNA (□,○), CT DNA (▵,▿), ML DNA (⋄,⊲), (C) Plot of ΔGO and ΔHO versus TΔSO of putrescine with CP DNA (▪,•), EC DNA (▴,▾), ML DNA (♦,◂) and (D) Plot of ΔGO and ΔHO versus TΔSO of cadaverine with CP DNA (□,○), EC DNA (▵,▿), ML DNA (⋄,⊲).
Figure 5.
Plots of variation of salt dependent thermodynamic parameters.
(A) Plot of ln Ka versus ln [Na+] for the binding of spermine with CP DNA (▪), EC DNA (•), MLDNA (▴). Bar diagram describing the variation of magnitude of thermodynamics parameters at three salt concentrations for (B) CP DNA, (C) EC DNA and (D) ML DNA at 293.15 K.
Table 4.
ITC derived thermodynamic parameters for the binding of spermine to CP, EC and ML DNA at 293.15 K at different [Na+] concentrationa.
Figure 6.
Melting profiles of DNA and DNA polyamine complexes.
Optical melting profiles (upper panels) of (A) CP DNA (□), spermine-CP DNA(▵), spermidine-CP DNA (O), (B) EC DNA (□), spermine-EC DNA(▵), spermidine-EC DNA(O), (C) ML DNA (□), spermine-ML DNA(▵), spermidine-ML DNA(O). DSC melting profiles (lower panels) of (D) CP DNA (solid lines) (E) EC DNA (solid lines), (F) ML DNA (solid lines) and respective DNA–spermine complex (- - - -) and DNA-spermidine complex (….).
Table 5.
Thermal melting data and the binding constants from melting data at saturating concentrations of polyamines with CP DNA, EC DNA and ML DNAa.
Figure 7.
Displacement plots of ethidium bromide-DNA complexes by polyamines.
Relative fluorescence intensity decrease of ethidium bromide (1.2 μM)-DNA(12.0 μM) complex induced by the binding of (A) spermine with CP DNA(-▪-), EC DNA (-•-), ML DNA (-▴-) and (B) spermidine with CP DNA(-▪-), EC DNA (-•-), ML DNA (-▴-) conducted in 10 mM SHE buffer pH 7.0 at 293.15 K (Inset: The values of IC50 of CP, EC and ML DNA shown as a bar graph).
Figure 8.
Circular dichroism spectral titration of DNA-poyamine complexes.
Intrinsic CD spectra of (A) CP DNA (30 µM) treated with 0–63 µM (curves 1 to 7) spermine (B) CP DNA (30 µM) treated with 0–135 µM (curves 1 to 7 ) spermidine (C) EC DNA (30 µM) treated with 0–95 µM (curves 1 to 7) spermine (D) EC DNA (30 µM) treated with 0–175 µM (curves 1 to 7) spermidine (E) ML DNA (30 µM) treated with 0–120 µM (curves 1 to 7) spermine and (F) ML DNA (30 µM) treated with 0–250 µM (curves 1 to 7 ) spermidine at 293.15 K.