PHOSPHORESCENCE QUENCHING OF POLY rA IN GLUCOSE‐SODIUM ACETATE SOLUTION AT 77 K*

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Abstract. The phosphorescence of poly rA at 77 K in an aqueous medium containing glucose is half‐quenched by bound ethidium bromide at a fractional concentration, r1/2, of 0.005, and by bound proflavine at r1/2= 0.002: r1/2= 0.024 for Co2+ and r1/2= 0.039 for Mn2+. The decay of the dye‐quenched poly rA phosphorescence is markedly nonexponential and decays more rapidly with increasing dye concentration, while the decay of the metal‐ion quenched poly rA phosphorescence parallels that of the unquenched poly rA, independent of metal‐ion concentration. Förster overlap integrals and critical distances for transfer of both poly rA singlet and triplet excitation to dye singlet states are calculated, and used to explain a consistent interpretation of the experimental results in terms of one‐step direct excitation transfer from base to dye or metal ion in a highly folded polymer conformation.