Abstract
Binding of tetracationic porphyrin (TMPyP4+) to poly(rA) has been studied in neutral buffered solution of low ionic strength in a wide range of molar phosphate-to-dye ratios (P/D) using absorption spectroscopy, polarized fluorescence and fluorimetric titration. Two competitive binding modes were identified: partial intercalation of porphyrin chromophores between adenine bases prevailing at P/D > 20 and its outside binding to poly(rA) backbone dominating at P/D < 6. Both of them were accompanied by enhancement of the porphyrin emission. Absence of the emission quenching near stoichiometric P/D ratios allowed us to assume that external binding occurs without the self-stacking of the chromophores.
Published Version
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