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In the conjugated chromophores, the electrons jump between energy levels that are extended pi orbitals, created by electron clouds like those in aromatic systems. Common examples include retinal (used in the eye to detect light), various food colorings, fabric dyes (azo compounds), pH indicators, lycopene, β-carotene, and anthocyanins. Various ...
Haem, for example, is a biochrome responsible for the red appearance of blood. It is found primarily in red blood cells (erythrocytes), which are generated in bone marrow throughout the life of an organism, rather than being formed during embryological development. Therefore, erythrocytes are not classified as chromatophores.
Two examples of carotenoids are lycopene and β-carotene. These molecules also absorb light most efficiently in the 400 – 500 nm range. Due to their absorption region, carotenoids appear red and yellow and provide most of the red and yellow colours present in fruits and flowers. The carotenoid molecules also serve a safeguarding function.
This configuration change pushes against an opsin protein in the retina, which triggers a chemical signaling cascade, which results in perception of light or images by the brain. The absorbance spectrum of the chromophore depends on its interactions with the opsin protein to which it is bound, so that different retinal-opsin complexes will ...
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For example, the blue carotenoprotein, linckiacyanin has about 100-200 carotenoid molecules per every complex. [19] In addition, the functions of these pigment-protein complexes also change their chemical structure as well. Carotenoproteins that are within the photosynthetic structure are more common, but complicated.
During photochemical processes employing donor and acceptor chromophores in organic solar cells, a photon is absorbed by the donor and an exciton is generated. The exciton diffuses to a donor/acceptor interface, or heterojunction, where an electron from the lowest unoccupied molecular orbital of the donor is transferred to the LUMO of the acceptor. [7]
The phycobilins fluoresce at a particular wavelength, and are, therefore, often used in research as chemical tags, e.g., by binding phycobiliproteins to antibodies in a technique known as immunofluorescence. [4]