Single-Stranded Nucleic Acids As Templates For Porphyrin Assembly Formation

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Inorganica Chimica Acta


Resonance light scattering (RLS) and circular dichroism (CD) spectroscopies have been used to investigate the interactions of several cationic porphyrins with poly(dA) and poly(rA). Neither tetrakis(N-methylpyridinium-4-yl)porphin nor its zinc(II) derivative (H₂T4 and ZnT4) show any tendency to form extended porphyrin assemblies in the presence of poly(dA). However, the poly(dA) complex of CuT4 involves considerable porphyrin self-stacking. In the presence of poly(rA), only ZnT4 of these three porphyrin derivatives, fails to assemble. Differences in the interactions of trans-bis(N-methyl-pyridinium-4-yl)diphenylporphine (t-H₂Pagg) with these two single-stranded nucleic acid polymers are described. Whereas the porphyrin is capable of forming extended assemblies with either poly(dA) or poly(rA), increasing the salt concentration in the latter system results in a reversal of the induced circular dichroism spectrum in the Soret region indicating a conformational change of the porphyrin assembly.

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