Study of Complex Associates Between Cationic Porphyrins and Nucleosides or Nucleotides Magdalena Makarska, Stanisław Radzki Department of Inorganic Chemistry Maria Curie-Skłodowska University in Lublin

H 2 TMePyP 5,10,15,20-tetrakis[4-(1-methyl-4- pyridyl)]porphyrin  C 44 H 38 N 8 · 4(C 7 H 7 SO 3 ) = g/mol  violet powder, dark purple in solution

H 2 TTMePP 5,10,15,20-tetrakis[4- (trimethylamino)phenyl]porphyrin  C 84 H 90 N 8 O 12 S 4 = g/mol  dark red powder, red in solution

Molar absorbancy indexes Spectra of porphyrin complexes with copper (II) with copper (II)

Protonation of H 2 TTMePP porphyrin Four porphyrin acid-base equilibria

Scheme of interactions between porphyrins systems and nucleic bases and their derivatives and nucleic bases and their derivatives

Nucleic bases and their derivatives adenine adenosine ATP guanine guanosine GTP

thymine uracil uridine UTPCTP cytosine cytidine thymidine

The sites of metal fixation in nucleic bases adenine guanine thymine cytosine uracil

Association constants A - absorbancy; ε 0 - molar absorbancy index of initial porphyrin concentration; ε 1 and K 1,..., etc. - molar absorbancy indexes and gradual stability constants for complexes with stoichiometry 1:1, 1:2,..., etc; for complexes with stoichiometry 1:1, 1:2,..., etc; [N] - molar nucleic base (ligand) concentration; [P] - molar porphyrin concentration.

Titration experiments (pH=12.4)

Titration experiments (pH=12.7)

The absorbance changes in the function of porphyrin concentration of porphyrin concentration

Association constants

Conclusions 1. The big differences in the results for particular nucleic agents, and first of all for different pH values indicate the diversification of interaction level of investigated systems. Such results can be the proof ofmutual interactions porphyrin - nucleic ligand. 2. Interactions of H 2 TTMePP with nucleic bases are much stronger than interactions of H 2 TMePyP. Such effect is caused by the aniline group, much bigger than pyridyl group - “stacking” (specific interactions consisting in forming of associates by reacting molecules) between porphyrin and nucleic ligands is much more stronger for bigger compounds. 3. The results show that the more stable associates are formed at lower pH value. Moreover, the strength of the obtained associates increases in series:nucleic base  nucleoside  nucleotide, although many departures from the rule are observed, because of high diversity and different pH values of investigated systems. 4. The association constants for interactions between porphyrins and nucleic agents let us suppose that by means of adequate porphyrin substituent groups and metal ion in porphyrin cave it would be possible to control the level of interactions between porphyrins and complicated DNA systems and, probabely, introduce metalloporphyrins to the desirable place of DNA chain. 5. However, the substitution reactions proceeding on the metallic centres connected with nucleic acids are much more complicated, what is caused by the interactions of ligands with other groups, as well as conformational changes in a macromolecule. Therefore all data obtained during study of porphyrin - DNA interactions should be particularly considered, because some porphyrin systems can join and interact with DNA in different ways, depending on neighbouring chemical compounds. Very often the manner of interactions between reagents is determined by the kind of reaction buffer and ionic strength connected with environment of investigated system.

Metalloporphyrin molecule incorporated in DNA chain