We have considered the formation of the liquid-crystalline dispersions (LCD) as a result of the Chitosan and the DNA molecules binding. By means of the circular dichroism (CD) the formation efficiency of Chitosan-DNA complexes upon the properties of both the Chitosan molecules and the solvent (ionic strength) was investigated. A model of the Chitosan binding to DNA capable of describing the formation of LCD as a process of DNA condensation under equilibrium binding of Chitosan to DNA was explored (1). At a certain Chitosan concentration, DNA molecules with different numbers of bound ligands can be found in equilibrium in the solution. If the number of Chitosan ligands covering the DNA molecule exceeds a certain ?critical? value, this molecule will transit to a different state and will be able to interact and form LCD. We suggest that this ?critical? value corresponds to degree of negative charge neutralization necessary for DNA condensation induced by Chitosan and hence depends on ionic strength of solution. Using the Mannings counterion condensation theory (2) the factor of charge neutralization was evaluated and the ?critical? value was calculated. This approach give us opportunity to estimate the dependence of intrinsic binding constant for Chitosan-DNA interactions on the ionic strength.

References and Footnotes

1. Nechipurenko, Yu. D., Wolf, A. M., Salyanov, V. I., Yevdokimov, Yu. M. J. Experimental and Theoretical Physics 98, 93-101 (2004).
2. Manning, G. S. Q. Rev. Biophys. 11, 179-246 (1978).