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The Chromophores,
Spectroscopy, and Photochemistry of Human Ocular Lipofuscin
Simon, John1,
Lamb, Laura1, Haralampus-Grynaviski, Nicole1
and Sarna, Tadeusz2
Duke University, Durham, NC1
Jagiellonian University, Krakow, Poland2
Abstract-
To probe the molecular constituents of lipofuscin, intact granules isolated
from human RPE cells were extracted using a chloroform:methanol (2:1)
solvent mixture and the resulting polar and nonpolar solvent layers
were studied by mass spectrometry and optical spectroscopy. The optical
properties of the extract are similar to that of the intact granules.
Mass spectrometric analysis is used to identify molecular species present
in the extract. In addition to A2E and phospholipids, retinyl palmitate
is established as an emissive component of the extract. Studies of A2E
suggest that this molecule is not likely to be the origin of the phototoxic
behavior of lipofuscin. AFM and optical emission microscopy are used
to examine the morphology and emission properties of intact lipofuscin
granules. A correlation is observed between the emission maximum and
the emission width of individual granules. Complicated photobleaching
dynamics are observed. While there is variability in the emission properties
of individual granules, no spatial dependence of the emission spectrum
is observed within single granules.
Keywords: lipofuscin,
phototoxicity, A2E, macular degeneration
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