Investigation of competitive binding of two ligands: Actinocin antibiotic and caffeine to DNA
Keywords:
spectrophotometry, DNA, actinocin antibiotics, binding entropy, enthalpy, caffeine, binding constantsAbstract
Binding of actinocin antibiotic ActIII to DNA without and in presence of caffeine was investigated at different temperatures in 8·10-2 M NaCl by VIS- and UV-spectroscopy. Observed concentration dependences in both systems were analysed in according with the different models of binding. We used the DALSMOD optimisation program to calculate association constants and thermodynamic parameters of binding in the systems DNA-ActIII and DNA-ActIII-caffeine. Decrease of both constants of binding antibiotic to DNA in presence of caffeine were shown. Constant of association caffeine to DNA was calculated by using the model of competitive binding. It is about 820 M-1. The values of DH and DS for different types of complexes, which were calculated by using Vant Goff's method, changed in presence of caffeine. The values of DS for the second type of complex changed from -9,4 e.u. to +9.8 e.u.
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