ACTA BIOLOGICA CRACOVIENSIA

16 TH INTERNATIONAL SYMPOSIUM ON CAROTENOIDS
2.5.
Antioxidant properties of carotenoids in model
pigment-protein systems
Aleksandra Sulikowska1 , Aleksandra Orzechowska1 ,
Leszek Fiedor2 , Kvetoslava Burda1 , Joanna Fiedor1 1 Department of Medical Physics and Biophysics, Faculty of Physics
and Applied Computer Science, AGH-University of Science and
Technology, 30-059 Krakow, Mickiewicza 30, Poland,
aleksandra.sulikowska@gmail.com,
orzechowska@novell.ftj.agh.edu.pl, burda@novell.ftj.agh.edu.pl,
fiedor@novell.ftj.agh.edu.pl
2 Department of Plant Physiology and Biochemistry, Faculty of
Biochemistry, Biophysics and Biotechnology, Jagiellonian
University, 30-387 Krakow, Gronostajowa 7, Poland,
leszek.fiedor@uj.edu.pl
Carotenoids are structurally and functionally a very diverse group
of isoprenoid pigments. They occur commonly in all photosynthetic
organisms carrying out diverse functions. Apart from light
harvesting and structural function (photo)protection is considered
as one of their most important role, however still not fully
understood. Carotenoids are well known physical quenchers of
chlorophyll excited states and reactive oxygen species. They also
act as efficient chemical quenchers of reactive species undergoing
irreversible modifications (Fiedor et al., 2005).
In the present study we investigated the protective role of
carotenoids toward chemically oxidised (bacterio)chlorophylls in
model pigment-protein complexes. In this approach a series of
model LH1 complexes was prepared with carotenoids that significantly
differed in structure (i.e. length of their C=C bonds, presence
of additional side groups), following a recently developed
method (Fiedor et al., 2004). For oxidation reactions various concentrations
of either potassium ferricyanide or hydrogen peroxide
was used. The progress of oxidation reaction of model LH1 complexes
was monitored by following the changes in their UV-VIS
absorption, fluorescence and thermoluminescence spectra.
Oxidation of model pigment-protein complexes with either potassium
ferricyanide or hydrogen peroxide leads to irreversible
changes in their absorption spectra indicating progressive
decomposition of the pigments. The changes in absorption spectra
are paralleled with the decrease of emission intensity in fluorescence
spectra and a temperature shift observed in thermoluminescence
spectra. Our results indicate that carotenoid presence
do affect the stability of a complex exposed to chemical oxidation.
The most stable are complexes reconstituted with longchain
carotenoids.
REFERENCES
FIEDOR J, FIEDOR L, HEASSNER R, SCHEER H. 2005. Cyclic endoperoxides
of β-carotene, potential pro-oxidants, as products of chemical
quenching of single oxygen. Biochim. Biophys. Acta 1709: 1-4.
FIEDOR L, AKAHANE, J, KOYAMA Y. Carotenoid-induced cooperative formation
of bacterial photosynthetic LH1 complex. Biochemistry
43: 16487-16496.
2.6.
The influence of carotenoid population on
the structure and fluorescence emission
properties of the LH2 light-complex from
Rhodopseudomonas palustris
Andrew Gall 1 , Trjaart Krüger 2 , Cristian Ilioaia 2 ,
Rienk van Grondelle 2 , Bruno Robert 1
SESSION 2
1 CEA, Institute of Biology and Technology of Saclay, URA 2096
CNRS, 91191 Gif sur Yvette, France, andrew.gall@cea.fr,
bruno.robert@cea.fr
2 Department of Physics and Astronomy, Faculty of Sciences, Vrije
Universiteit, Amsterdam, De Boelelaan 1081 HV Amsterdam,
The Netherlands, t.p.j.kruger@vu.nl, c.ilioaia@vu.nl,
r.van.grondelle@vu.nl
It is known that varying the growth conditions of purple photosynthetic
bacteria different carotenoids may be incorporated into
the light-harvesting (LH) complexes. This can be achieved by
either culturing the cells under different light regimes, or in the in
the presence of diphenylamine (DPA) which inhibits the activity of
phytoene desaturase. We will present our recent work on the
influence of carotenoid type on the structure and fluorescence
properties of isolated LH2 molecules.
2.7.
Excitation energy dependence of intramolecular
charge transfer dynamics of fucoxanthin
Daisuke Kosumi1,2 , Ritsuko Fujii1,2 , Mitsuru Sugisaki1,2,3 ,
Masahiko Iha 4 , Harry A. Frank5 , Hideki Hashimoto1,2,3 1The Osaka City University Advanced Research Institute for
Natural Science and Technology (OCARINA), 3-3-138 Sugimoto,
Sumiyoshi-ku, Osaka 558-8585, Japan
2CREST/JST, 4-1-8 Hon-chou, Kawaguchi, Saitama 332-0012,
Japan
3Department of Physics, Graduate School of Science, Osaka City
University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585,
Japan
4South Product Co. Ltd., 12-75 Suzaki, Uruma-shi, Okinawa
904-2234, Japan
5Department of Chemistry, University of Connecticut, Storrs,
CT 06269-3060, USA
Carotenoids containing a carbonyl group in conjugation with their
polyene backbone are naturally-occurring pigments in marine
organisms and are essential to the photosynthetic light-harvesting
function in aquatic algae. These carotenoids exhibit spectral characteristics
attributed to an intramolecular charge transfer (ICT)
state that arise in polar solvents due to the presence of the carbonyl
group. In this study, we report the spectroscopic properties
of the carbonyl containing carotenoid fucoxanthin in polar
(methanol) and nonpolar (cyclohexane) solvents investigated by
steady-state absorption and femtosecond pump-probe measurements.
Transient absorption associated with the optically forbidden
S 1 (2 1 Ag – ) state and/or the ICT state were observed following
one-photon excitation to the optically allowed S 2 (1 1 B u + ) state in
methanol. The transient absorption measurements carried out in
methanol showed that the ratio of the ICT-to-S 1 state formation
increased with decreasing excitation energy. We also showed that
the ICT character was clearly visible in the steady-state absorption
in methanol based on a Franck-Condon analysis. The results
suggest that two spectroscopic forms of fucoxanthin, blue and
red, exist in the polar environment.
38 ACTA BIOLOGICA CRACOVIENSIA Series Botanica