Application to Some Biomolecular Systems

Ionic Atmosphere around DNA and Direct Visualization of the Thermal Transconformation (Helix- Coil Transition) 

The DNA polyelectrolyte behavior is expressed by the charge parameter (G. S. Manning ) see also the review. Reference 54. 

In the Manning model, if 1, the DNA is thermodynamically unstable and the counterions will condense on it until reaches the value of unity. When = 1, l=b theoretically this situation corresponds to an extended DNA backone-and b corresponds almost to the Landau length. In the temperature range 20-80°C, the Landau length does not vary 

FIGURE 8. The rodlike DNA model , phosphate sites 0, counterions , coions b is the distance between two neighbor phosphate sites projected onto the cylindrical axis. 

Let Hg and be the molar concentrations of phosphate sites and added salt, respectively. In his model Manning calculated the following expressions for and Ihe activity coefficients of the counterions and coions 

---