Article

Origins of life and evolution of the biosphere

, Volume 20, Issue 3, pp 321-330

Protoporphyrin ix as a possible ancient photosensitizer: Spectral and photochemical studies

  • G. I. LozovayaAffiliated withN. G. Kholodny Institute of Botany, Ukr. SSR Academy of Sciences
  • , Z. MasinovskyAffiliated withLaboratory of Evolutionary Biology, Czechoslovak Academy of Sciences
  • , A. A. SivashAffiliated withN. G. Kholodny Institute of Botany, Ukr. SSR Academy of Sciences

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Abstract

Due to the potential special position of protoporphyrin IX in the evolution of photosynthesis, the absorption and fluorescence characteristics of this pigment and its complexes with human serum albumin (HSA) and basic proteinoid have been studied in parallel with their photochemical activity. The most significant change in the absorption spectrum of PP IX was the appearance of a new maximum at 455 (or 461) nm in the presence of HSA or proteinoid respectively. Some changes in the physicochemical properties of PP IX in different microenvironments have been detected by changes in fluorescence emission and excitation spectra (intensity, quantum yields, position of maxima). The increase of fluorescence quantum yield resulting from the formation of PP IX complexes with HSA or proteinoid correlates with the increase of their photochemical activity. Results obtained are discussed from the point of view of the early evolution of the photosynthetic apparatus.