Articolo in rivista, 1995, ENG, 10.1111/j.1751-1097.1995.tb05259.x
F. Lenci, N. Angelini, F. Ghetti, A. Sgarbossa, A. Losi, A. Vecli, C. Viappiani, P. Taroni, A. Pifferi, R. Cubeddu
Istituto Biofisica CNR, Via S. Lorenzo 26, 56127 Pisa, Italy Dipartimento Fisica Universita, V, le Scienze, 43100 Parma, Italy CEQSE CNR e Dip. Fisica Politecnico, P. le Da Vinci, 20131 Milano, Italy
In photoresponsive ciliates, like Blepharisma japonicum and Stenter coeruleus, the photoreceptor pigments responsible for photomotile reactions are hypericin-type chromophores packed in highly osmiophilic subpellicular granules. Liposomes loaded with hypericin can constitute a simple model system, appropriate for understanding the primary light-induced molecular events triggering the sensory chain in these microorganisms. Optical absorption, steady-state and time-resolved fluorescence and pulsed photoacoustic calorimetry have been used to measure spectral distributions, fluorescence lifetimes, radiative and radiationless transition quantum yields of hypericin when assembled into egg L-alpha-phosphatidylcholine liposomes. With respect to hypericin ethanol solutions, both absorption and fluorescence maxima are 5 nm red shifted when the pigment is inserted into the lipidic microenvironment, regardless of the hypericin local concentration. Increasing by 100 times the hypericin local concentration decreases the relative fluorescence quantum yield by a factor of around 150 and the fraction of thermally released energy, conversely, increases from 0.6 to 0.9. From the analysis of fluorescence lifetimes and their relative amplitudes it appears that a subnanosecond living component is predominant at the highest hypericin local concentrations.
Photochemistry and photobiology 62 (1), pp. 199–204
Cubeddu Rinaldo, Pifferi Antonio Giovanni, Taroni Paola, Viappiani Cristiano, Sgarbossa Antonella, Angelini Nicola, Lenci Francesco, Ghetti Francesco
ID: 266818
Year: 1995
Type: Articolo in rivista
Creation: 2013-10-27 16:16:50.000
Last update: 2022-11-17 15:51:50.000
CNR institutes
External IDs
CNR OAI-PMH: oai:it.cnr:prodotti:266818
DOI: 10.1111/j.1751-1097.1995.tb05259.x
ISI Web of Science (WOS): A1995RJ71000029