Photophysical Properties of Thionine and Methylene Blue When Bound to Dna, Polynucleotides or Nucleotides
1992; Taylor & Francis; Linguagem: Inglês
10.1007/978-94-011-2492-8_24
ISSN1061-0278
AutoresJohn M. Kelly, Eimer Tuite, Wilhelm J. M. van der Putten, Godfrey S. Beddard, Gavin D. Reid,
Tópico(s)Photochromic and Fluorescence Chemistry
ResumoThe photophysical properties of methylene blue and thionine in the presence of DNA, polynucleotides and mononucleotides have been studied by emission spectroscopy and transient absorption measurements. The singlet state fluorescence yield and lifetime for each of the dyes is reduced upon binding to guanine-containing polynucleotides or to deoxyguanosine monophosphate. The quenching, which is attributed to photo-induced electron transfer, is extremely rapid (4 ps and 0.8 ps for methylene blue and thionine respectively when bound to poly[d(G-C)].poly[d(G-C)]). Thionine, but not methylene blue, is strongly quenched by adenine derivatives, consistent with the higher oxidising potential of its singlet excited state. Transient absorption measurements show that even on a picosecond timescale yields of reduced dye and oxidised guanine formed are very low.
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