Nucleic Acids Research, 1986, Vol. 14, No. 14 5919-5931
© 1986
Articles |
The influence of ionic strength on the binding of a water soluble porphyrin to nucleic acids
Department of Chemistry, Swarthmore College Swarthmore, PA 19081 1Department of Chemistry, Goucher College Towson, MD 21204, USA 2CNR Center of Molecular Biology, University of Rome 00185 Rome, Italy
*To whom correspondence should be addressed
Received March 13, 1986. Revised June 19, 1986. Accepted June 19, 1986.
The ionic strength dependences of the binding of tetrakis (4-N-methypyridyl)porphine (H2TMpyP) to poly(dG-dC) and calf thymus DNA have been determined. For the former system the results are typical of other Intercalators, i.e., a plot of log K vs log [Na+] is linear albeit with a slope which suggests that the "effective charge" of the porphyrin is closer to two than the formal charge of +4. For calf thymus DNA, the binding profile is not completely compatible with the predictions of condensation theory. Whereas the avidity of binding does decrease with increasing [Na+] as predicted, of greater interest is the relocation of the porphyrin from GC-rich regions to AT-rich regions as the ionic strength increases.