The simulation of the binding processes of actinocin antibiotics to DNA at different ionic strength and temperatures
Keywords:
spectrophotometry, DNA, actinocin antibiotic, effects of ionic strength, melting curves, entropy and enthalpy of complexationAbstract
Spectral properties of actinocin antibiotic in complexes with DNA have been studied by UV-visible spectrophotometry. Two binding models with one and two binding sites for McGhee and von Hippel equations with different values of parameters have been considered. To choose the optimal model of complexation the optimization program of spectrophotometric concentration dependencies DALSMOD have been used. Using this program we can conclude, that as minimum three complexes with different absorption spectra in the system ActII - DNA are present. The logarithms of K2 and K3 for DNA-ActII mixtures, calculated for models I and II, in different sodium ion concentration were in good agreement with predictions of the counterion condensation theory. Via analysis of the absorption spectra of ActII-DNA mixtures at different temperatures, we obtained the values of AH and AS for each type of complexes. The magnitudes of entropy AS were positive in the 2·10-2 M NaCl solution and negative in the 0.15 M NaCl solution.
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