spectrophotometric study of water

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STUDY OF Cu(II) INFLUENCE ON INTERACTIONS BETWEEN
WATER-SOLUBLE PORPHYRINS AND URACIL, URININE OR
UTP
Magdalena MAKARSKA and Stanisław RADZKI
DEPARTMENT OF INORGANIC CHEMISTRY
Specific interactions of water-soluble porphyrins and their metal complexes
with nucleic acids building blocks, as purines and pyrimidines, and their nucleoside
or nucleotide derivatives, can lead either to formation of new biological systems or to
destruction of polynucleotide structure of DNA [1-4]. Precise analysis of the systems
mentioned above could be used not only for better understanding of the
macromolecules behaviour in water solutions, but also for application purposes, for
example in photodynamic therapy of cancer (PDT) [5]. Metal complexes of
porphyrins can be also utilized as cleavage agents using during investigation of
nucleic acids tertiary structure, which is helpful in the study of different drugs and
enzymes functioning [6].
The results introduced here are the continuation of experiments carried out
last year, and refer to the spectrophotometric investigation of nucleic agent-porphyrin
complex formation. The present work was concerned on the copper complexes of
two
water-soluble
cationic
porphyrins:
tetrakis[4-(trimethylammonio)phenyl]
(CuTTMePP) and tetrakis (1-methyl-4-pyridyl) (CuTMePyP). As nucleic agents
uracil, urydine and UTP were selected. Absorption spectra were taken with an
SPECORD M42 (Carl Zeiss Jena) spectrophotometer using quartz cells, to record
spectra between 200 and 900 nm at the temp. of 21C. Spectra were registered
digitally under the control of the program M500 running on PC. The measurements
were conducted in two different pH conditions, as is known that the reaction of
solution has an influence on degree of association [7].
As the conclusion of our studies we found that the strength of association
between copper metalloporphyrins and nucleic agent increases in row: nucleic basenucleoside-nucleotide, as in the case of interactions between free porphyrins and
nucleic compounds. What is more, association constants between pyrimidines and
Cu(II) complexes are much higher than constants calculated for systems pyrimidinefree porphyrin – this fact testify for formation of the bond, between donor oxygen
atoms of pyrimidine bases and the central atom Cu(II), which has an influence on the
strenght of generated associates.
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Fig. 1. The results of fitting procedure concerning the absorbance changes of Soret band during the
titration of CuTTMePP complex by uracil, uridine and UTP, at pH = 12.4 and 12.7. The
black points represent experimental data, whereas the curves are generated by the fitting
procedure.
References:
1. R. F. Pasternack, E. J. Gibbs, A. Gaudemer; J. Am. Chem. Soc., 1985, 107, 8179.
2. R. F. Pasternack, E. J. Gibbs, J. J. Villafranca; Biochemistry, 1983, 22, 5409.
3. P. Kubat, K. Lang, P. Anzenbacher; J. Chem. Soc., Perkin Trans. 1, 2000, 933.
4. M. Tabata, M. Sakai, K. Yoshioka; Analytical Sciences, 1990, Oct, 6, 651.
5. K. Driaf, R. Granet, P. Krausz; Can. J. Chem., 1996, 74, 1550.
6. G. Pratviel, J. Bernadou, B. Meunier; Angew. Chem. Int. Ed. Engl., 1995, 34,
746.
7. M. Sirish, H. J. Schneider; Chem. Commun., 2000, 23.
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