Table 1.
Features of major chromophores or pigments in the mitochondria or the retina.
| Chromophores∗ or pigments | Wavelength absorption maxima (nm) | Molecular or cellular localizations | Roles in the blue light hazard | References | ||
|---|---|---|---|---|---|---|
| Mitochondria | Flavin | FMN | 450 | Complex I | Pro-† | [128, 216] |
| FAD | Complex II | |||||
| Porphyrin | Hemes | 400-410 | Complex III | [135, 217, 218] | ||
| Cytochrome c oxidase (complex IV) | ||||||
| Cytochrome P450 | ||||||
| Retina | Blue-cone opsin‡ (OPN1SW) | 430 | Outer segments of cones | [79, 219] | ||
| Rhodopsin (OPN2) | 500 | Outer segments of rods | [220, 221] | |||
| Melanopsin (OPN4) | 479 | Cell membrane of ipRGCs | [222, 223] | |||
| All-trans-retinal | 382 | POS; phagocytosed POS in RPE | [78, 224] | |||
| A2E§ | 336, 430-439 | Lipofuscin in RPE cells | [225, 226] | |||
| Melanin | 335 | Melanosomes in RPE cells | Anti-/pro- | [86, 98, 227] | ||
| Carotenoid | Lutein | 450 | HL and OPL in the peripheral retina | Anti-† | [228–231] | |
| Zeaxanthin | HL and OPL in the macula | |||||
Abbreviations: FMN: flavin mononucleotide; FAD: flavin adenine dinucleotide; complex I: NADH dehydrogenase; complex II: succinate dehydrogenase (SDH); complex III: coenzyme Q – cytochrome c reductase; OPN: opsin; POS: photoreceptor outer segments; HL: Henle's nerve fiber layer, composed of photoreceptor axons; OPL: outer plexiform layer. ∗The (part of the) molecule that absorbs the radiation and accounts for its color is dubbed the chromophore. †Pro- refers to the corresponding chromophore or pigment that can mediate the blue light hazard, while anti- refers to a protective effect against the blue light hazard. ‡Cone opsins include three visual pigments, which are sensitive to blue light (peak at 430 nm), green light (peak at 540 nm), and red light (peak at 570 nm), respectively. §A2E is one of the components and the potent photosensitizers of lipofuscin. Absorption spectrum of A2E is featured by two maxima at 336 and 430–439 nm.