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In many species of animals, red carotenoid-based coloration is produced by metabolizing yellow dietary pigments, and this red ornamentation can be an honest signal of individual quality. However, the physiological basis for associations between organism function and the metabolism of red ornamental carotenoids from yellow dietary carotenoids remains uncertain. A recent hypothesis posits that carotenoid metabolism depends on mitochondrial performance, with diminished red coloration resulting from altered mitochondrial aerobic respiration. To test for an association between mitochondrial respiration and red carotenoids, we held wild-caught, molting male house finches in either small bird cages or large flight cages to create environmental challenges during the period when red ornamental coloration is produced. We predicted that small cages would present a less favorable environment than large flight cages and that captivity itself would decrease both mitochondrial performance and the abundance of red carotenoids compared to free-living birds. We found that captive-held birds circulated fewer red carotenoids, showed increased mitochondrial respiratory rates, and had lower complex II respiratory control ratios—a metric associated with mitochondrial efficiency—compared to free-living birds, though we did not detect a difference in the effects of small cages versus large cages. Among captive individuals, the birds that circulated the highest concentrations of red carotenoids had the highest mitochondrial respiratory control ratio for complex II substrate. These data support the hypothesis that the metabolism of red carotenoid pigments is linked to mitochondrial aerobic respiration in the house finch, but the mechanisms for this association remain to be established.
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Fluorescence of carotenoids: Probing binding site interactions and conformational motion in carotenoproteins
The function of carotenoids in carotenoproteins is optimized by the electrostatic and steric interactions between the carotenoid and its surrounding binding site, which generally imposes distorted conformations and induces charge-transfer character. This chapter shows how the line shape of the fluorescence spectrum, the fluorescence quantum yield, and the fluorescence anisotropy of the second excited singlet state of a carotenoid, S2, can be used as probes of the structure and dynamics of carotenoids in carotenoproteins. The experimental approach and a brief introduction to the theory we used to detect hydrogen bonding interactions by ketocarotenoids in the orange carotenoid protein are introduced as an example. The fluorescence anisotropy is then introduced as a probe of a carotenoid’s excited-state conformational motion using results from a study of β-carotene in solution over a range of temperatures.
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- Award ID(s):
- 1904655
- PAR ID:
- 10630085
- Publisher / Repository:
- Elsevier
- Date Published:
- Page Range / eLocation ID:
- 85 to 111
- Subject(s) / Keyword(s):
- carotenoids carotenoproteins
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Book Chapter:
- https://doi.org/10.1016/bs.mie.2022.04.007
