Spectroscopical properties of porphyrin - melanin in polyvinyl alcohol film

Izabela Hanyz1, Alina Dudkowiak1, Tadeusz Sarna2, Danuta Wróbel1*

1Department of Molecular Physics, Institute of Physics, Poznan University of Technology, Piotrowo 3, 60-965 Poznan, Poland

2Department of Biophysics, Institute of Molecular Biology, Jagiellonian University, Al. Mickiewicza 3, 31-120 Kraków, Poland

* corresponding author

  • INTRODUCTION

    Porphyrin dyes play an essential function in some processes in the nature:

    • in photosynthesis: chlorophyll and its chemical derivatives play an essential function in charge separation and electron transport process and can serve as an exelent example of the using of chlorin and porphyrin dyes in the light conversion phenomena
    • in photoelectric devices: in which light energy can be converted into electric energy
    • in photodynamic therapy (PDT): of cancer as photosensitizers. In PDT porphyrin dyes and light are used for destruction of tumour cells

    Natural melanin is biological biopolymer

    • that in humans can be found in the skin, hair, eyes and also in the midbrain and inner ear
    • it plays a key role in photoprotection of some human cells against  damage by solar radiation
    • which is very difficult to be spectroscopically characterized and thus dihydroxylphenylalanine (dopa) melanin is used as a model in a lot of experiments

    Light energy absorbed by the dye molecules can be deactivated as a result of the radiative and non-radiative processes: fluorescence, delayed luminescence, thermal deactivation which are competitive to electron transport. The quantum yields of these processes depend on the spectroscopic dye forms.

    The aim of this paper is to study the radiative and non-radiative deexcitation of photoexcited states of two porphyrins: TAP (tetraaminoporphyrin), TPPS4 (tetraphenylsulphporphyrin) without and with dopa melanin embedded in PVA film.

    The new results are compared to the spectroscopic properties of TAP and TPPS4 in phosphate buffer solution studied previously [D. Wróbel, A. Planner, I. Hany , A. Wielgus, T. Sarna: "Porphyrin - melanin interaction monitored by delayed luminescence and photoacoustics", J. Photochem.Photobiol. - in press].