COMPLEX-FORMATION BETWEEN GADOLINIUM(III) PORPHYRINS AND SOME NUCLEICBASES OR THEIR NUCLEOSIDE DERIVATIVES IN AQUEOUS-SOLUTIONS

The mutual interactions of Gd(III)tetraphenylporphyrin (GdTPP), Gd(III )tetramethylpyridylporphyrin (GdTMePyP), and the free base tetramethyl pyridylporphyrin (H(2)TMePyP) with some nucleic bases (adenine, thymin e, uracil, and cytosine) and their N-glycoside derivatives (adenosine, thymidine, uridine, and cytidine) have been studied by spectrophotome tric titration in mixed methanol-ammonia-water solutions. It has been found that tetramethylpyridylporphyrin and its gadolinium complex form 1:1 complexes with nucleic bases and their nucleoside derivatives. Th e equilibrium constants were estimated using curve fitting procedures. The interactions are stronger for nucleoside derivatives than for nuc leic bases. They are also stronger for metallated than for nonmetallat ed porphyrins.