1 August 2003 Photophysical Properties of Xanthophylls in Carotenoproteins from Human Retina
Helena H. Billsten, Prakash Bhosale, Alexander Yemelyanov, Paul S. Bernstein, Tomáš Polívka
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The macula of the human retina contains high amounts of the xanthophyll carotenoids lutein and zeaxanthin [a mixture of (3R,3′R)-zeaxanthin and (3R,3′S-meso)-zeaxanthin]. Recently, it was shown that the uptake and the stabilization of zeaxanthin and lutein into the retina are likely to be mediated by specific xanthophyll-binding proteins (XBP). Here, we have used femtosecond pump–probe spectroscopy to study the dynamics of the S1 state of these xanthophylls in xanthophyll-enriched and native XBP. The results from the native XBP and the enriched XBP were then compared with those for carotenoids in organic solvents and in detergent micelles. Steady-state and transient absorption spectra show that the incorporation of xanthophylls into the protein causes a redshift of the spectra, which is stronger for lutein than for zeaxanthin. The transient absorption spectra further indicate that a part of the xanthophylls remains unbound in the xanthophyll-enriched XBP. The transient absorption spectra of the native XBP prove the presence of both xanthophylls in native XBP. Although the S1 lifetime of lutein does not exhibit any changes when measured in solution, micelles or XBP, we have observed the influence of the environment on the S1 lifetime of meso-zeaxanthin, which has a longer (12 ps) lifetime in XBP than in solution (9 ps). The most pronounced effect was found for vibrational relaxation in the S1 state, which is significantly slower for xanthophylls in XBP compared with micelles and solution. This effect is more pronounced for meso-zeaxanthin, suggesting a specific site of binding of this carotenoid to XBP.

Helena H. Billsten, Prakash Bhosale, Alexander Yemelyanov, Paul S. Bernstein, and Tomáš Polívka "Photophysical Properties of Xanthophylls in Carotenoproteins from Human Retina," Photochemistry and Photobiology 78(2), 138-145, (1 August 2003). https://doi.org/10.1562/0031-8655(2003)078<0138:PPOXIC>2.0.CO;2
Received: 17 December 2002; Accepted: 1 May 2003; Published: 1 August 2003

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