Singlet oxygen quenching by beta-carotene in HeLa cells

GABRIELA BOSIO; FRANCES BLAIKIE; THOMAS BREITENBACH; BRIAN PEDERSEN; PETER OGILBY; DANIEL MARTIRE

La Plata

Encuentro; Primera Reunión de Fotobiólogos Moleculares Argentinos; 2011

Universidad Nacional de La Plata

In this 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, 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.