Xanthophyll cycle reactions, where antheraxanthin is an intermediate stage, are usually responses to changes in light or radiation exposure, which cause changes in the internal pH of thylakoids.
The pigments that carry the brilliant colors _ carotene and xanthophyll _ are in the leaves all summer, but their presence is masked by the green chlorophyll that trees make during photosynthesis.
There are over 600 known carotenoids; they are split into two classes, xanthophylls ( which contain oxygen ) and carotenes ( which are purely hydrocarbons, and contain no oxygen ).
"' Rhodoxanthin "'is a xanthophyll pigment with a purple color that is found in small quantities in a variety of plants including " Taxus baccata ".
The conformational changes are stimulated by a combination of transmembrane proton gradient, the PsbS subunit of photosystem II and the enzymatic conversion of the carotenoid violaxanthin to zeaxanthin ( the xanthophyll cycle ).
He found that he could extract some pigments ( such as orange carotenes and yellow xanthophylls ) from leaves with non-polar solvents, but others ( such as chlorophyll ) required polar solvents.
The chloroplasts of " Bangia ", like others in the division Rhodophyta, contain chlorophyll a and sometimes chlorophyll d, as well as accessory pigments such as phycobilin pigments and xanthophylls.
?-carotene, due to their single retinyl group ( ?-ionone ring ), also have some vitamin A activity ( though less than ?-carotene ), as does the xanthophyll carotenoid ?-cryptoxanthin.
Since they are hydrocarbons, and therefore contain no oxygen, carotenes are fat-soluble and insoluble in water ( in contrast with other carotenoids, the xanthophylls, which contain oxygen and thus are less chemically hydrophobic ).
Most dinophyte chloroplasts contain at least the photosynthetic pigments " beta "-carotene, and at least one dinophyte-unique xanthophyll ( peridinin, dinoxanthin, or diadinoxanthin ), giving many a golden-brown color.