Book of Abstracts: Albany 2009
June 16-20 2009
© Adenine Press (2008)
Binding of new Ag-containing porphyrins with DNA. The influence of pH
The water-soluble porphyrins and their derivatives comprise an important class of compounds whose chemical and photochemical properties are widely exploited in both medical and biological applications. Therefore, many researchers attempt to study their interaction with DNA and create drugs on basis of porphyrins.
The interaction of three new cationic meso-tetra(4N-allylpyridyl)porphyrin [AgTAlPyP4], meso-tetra(4N-butylpyridyl)prophyrin [AgTButPyP4] and meso-tetra(4N-oxyethylpyridyl)porphyrin [AgTOEtPyP4] with Calf Thymus DNA at different pH has been investigated by Circular Dichroism (CD) and UV/visible-spectrophotometric methods. The changes in absorption spectra of porphyrins (at Soret region) in the presence of DNA at different temperatures were measured. From these dependence the binding constant, K, and stoichiometry, n, were calculated using McGhee and von Hippel equation. Further based on temperature dependence of K thermodynamic parameters of binding (free energy, enthalpy and entropy) were calculated.
The investigations of obtained data shows that the decrease of pH from 7.3 to 5 leads to changes of the sign of binding enthalpy from positive (unfavorable) to negative (favorable). These changes can account for the binding mode change affected by pH. The favorable enthalpy and the sign on induced CD spectra registered at lower pH lets us to conclude that under the low pH buffer conditions these porphyrins tend to bind with DNA via intercalation.
A. A. Ghazaryan1
1Yerevan State University,