Theorerical stidies of the water structurein dilute aqueous solution and conformational study ofdaunomycin

Abstract

The thermodynamic properties of dilute aqueous solution are influenced by the interactions between ions and water molecules as well as the change of the water structure around the ion. To obtain the hydration energies of monoatomic ions and local water structures around the ions, we make use of the discrete-continuum method. The calculated values for the hydration energies of ions are in good agreement with experimental values. The hydration energies of monoatomic cations can be qualitatively correlated with the sum of the successive ionization potentials from its atomic state to the ionic state. From their correlations, we can classify various ions as three groups. It is also found that the main factors which determine the stability of water structures around the ions are the charges and dimensions of ions. The viscosity of dilute aqueous solution is affected by the interaction between ion and water molecules as well as the change of the water structure around the ion. In the significant structure theory, these interaction energies must be involved in sublimation energy which need to form the vacancy of molecular size. Viscosities of NaCl, KCl, KBr, and KI are obtained versus temperature and concentration. It is shown the temperature and concentration dependent of viscosity of dilute aqueous solution. Daunomycin, an anthracycline antibiotic, has been found to inhibit virus multiplication and shows considerable activity against tumors. The activity may be varied by conformational changes of daunomycin and the conformation changes are come from pucker of D-ring and variation of environments of daunomycin. We have carried out conformational analyses by using empirical potential function. We found that the optimum conformer of each state is altered form $\alpha$ conformer to $\beta$ conformer through the pathway having four local minima via the hydration and $Mg^{2+}$ binding. Our calculated results are good agreements with those of X-ray crystallography and biolo...