INVESTIGADORES
BOSIO Gabriela Natalia
congresos y reuniones científicas
Título:
Responses and quenching of Singlet Oxygen in subcellular location,
Autor/es:
GABRIELA BOSIO; THOMAS BREITENBACH; BRIAN PEDERSEN; FRANCES BLAIKIE; PETER OGILBY; DANIEL MARTIRE
Lugar:
Buenos Aires
Reunión:
Workshop; Third south American Workshop: New Trends in Advanced Fluorescence Microscopy Techniques. Dynamics through the microscope: Fluorescence correlation spectroscopy,; 2011
Institución organizadora:
Universidad Nacional de Buenos Aires
Resumen:
Whether the
lifetime of O2(a1Δg) in cells is shortened by
reactions with cellular molecules or reaches the inherent maximum value is
still unclear. However, even with the maximum lifetime, the diffusion radius is
only approximately 220 nm during three lifetimes (-5% O2(a1Δg) remaining), much shorter than cellular dimensions indicating that
the primary reactions of O2(a1Δg) will be subcellularly localized near the site of O2(a1Δg)
formation. [1]
Carotenoids
in light-harvesting complexes quench O2(a1Δg) and the D1 protein in the PSII reaction centers in chloroplasts appear to
protect plant tissues from O2(a1Δg) produced by chlorophyll photosensitization suggesting
that proximity to the site of O2(a1Δg) formation, rather than their
average concentration, allows effective quenching. [2]
In our work we
investigated the b-carotene quenching of singlet oxygen, O2(a1Δg),
sensitized by different dyes with different subcellular localization.
Fluorescence and Resonance Raman Microscopy
were used as non-invasive methods to investigate the subcellular localization
of b-carotene in HeLa cells. To improve the fluorescence emission of the
carotene, it was also synthesized carotene moiety covalently bonded to a
fluorescein derivative.
Using a variety of different sensitizers,
such as TMPyP, PPa, etc, the O2(a1Δg)
phosphorescence decay was monitored in cells suspensions, both in the absence
and presence of b-carotene. The results were compared to those obtained with other
singlet oxygen quenchers (bovine serum albumin (BSA), and sodium azide. The ability
of b-carotene
to quench the O2(a1Δg) signal depended on the sensitizer used. For
example when using a hydrophilic sensitizer, the hydrophobic b-carotene had
little effect on the O2(a1Δg) signal whereas hydrophilic sodium azide had a
large effect
However, for sensitizers localized in
thin hydrophobic membranes, b-carotene and sodium azide were both efficient quenchers of the O2(a1Δg) signal.
These data are consistent with the notion
that O2(a1Δg) formed in the bilayer can
diffuse out into hydrophilic domains. Quenching of O2(a1Δg) by
BSA, which is localized in the extracellular domain, indicates that O2(a1Δg) can also diffuse across the plasma membrane.
We can conclude that b-carotene is not only effective as an intracellular singlet oxygenquencher, but also serves as molecular probeto detect the
location of the Singlet Oxygen signal which has
an important application, for
example, in the effectiveness of curingdiseases based onphotodynamic therapy.