The interaction of 8-methoxypsoralen (8-MOP) with synthetic eumelanin was investigated using static and time-resolved fluorescence and pulsed photoacoustic calorimetry. Due to the strong overlap of the absorption bands of melanin and 8-MOP, a method is presented to account for the systematic errors introduced by the optical filter effect exerted by each absorbing species in the fluorescence and the photoacoustic measurements. As a preliminary step to the understanding of the nonradiative behavior of the psoralen-melanin complexes, the photoacoustic parameters of 8-MOP in various solvents were determined. Spectroscopic data indicate the absence of interaction at the ground-state level, whereas the singlet excited state of 8-MOP is quenched by the pigment; the average fluorescence lifetimes are independent of the melanin concentration, thus indicating a static quenching mechanism. The photoacoustic data show that the quenching process involves an increased intersystem crossing probability, which is almost unaffected by the presence of oxygen, as expected for a molecule essentially acting as a type I photosensitizing agent.

The interaction of melanin with 8-methoxypsoralen: effect on radiative and nonradiative transitions. A fluorescence and pulsed photoacoustic study / A. Losi; C. Viappiani; P.R. Crippa. - In: PHOTOCHEMISTRY AND PHOTOBIOLOGY. - ISSN 0031-8655. - 59(1994), pp. 596-602. [10.1111/j.1751-1097.1994.tb09662.x]

The interaction of melanin with 8-methoxypsoralen: effect on radiative and nonradiative transitions. A fluorescence and pulsed photoacoustic study

LOSI, Aba;VIAPPIANI, Cristiano;
1994

Abstract

The interaction of 8-methoxypsoralen (8-MOP) with synthetic eumelanin was investigated using static and time-resolved fluorescence and pulsed photoacoustic calorimetry. Due to the strong overlap of the absorption bands of melanin and 8-MOP, a method is presented to account for the systematic errors introduced by the optical filter effect exerted by each absorbing species in the fluorescence and the photoacoustic measurements. As a preliminary step to the understanding of the nonradiative behavior of the psoralen-melanin complexes, the photoacoustic parameters of 8-MOP in various solvents were determined. Spectroscopic data indicate the absence of interaction at the ground-state level, whereas the singlet excited state of 8-MOP is quenched by the pigment; the average fluorescence lifetimes are independent of the melanin concentration, thus indicating a static quenching mechanism. The photoacoustic data show that the quenching process involves an increased intersystem crossing probability, which is almost unaffected by the presence of oxygen, as expected for a molecule essentially acting as a type I photosensitizing agent.
The interaction of melanin with 8-methoxypsoralen: effect on radiative and nonradiative transitions. A fluorescence and pulsed photoacoustic study / A. Losi; C. Viappiani; P.R. Crippa. - In: PHOTOCHEMISTRY AND PHOTOBIOLOGY. - ISSN 0031-8655. - 59(1994), pp. 596-602. [10.1111/j.1751-1097.1994.tb09662.x]
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11381/2393136
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 7
  • ???jsp.display-item.citation.isi??? 7
social impact