Pigment

A pigment is a material that changes the colour of light through selective absorption and scattering, commonly while dispersed as particles in another material. Particle size and dispersion therefore matter alongside molecular or crystal composition.

Pigments include inorganic solids and organic materials such as melanin. Their colour is an optical property, while properties such as chemical stability and interaction with a binder determine how that colour survives in a coating or biological structure.

Melanin denotes a family of biological pigments formed through oxidative chemistry of aromatic precursors. It is not one small molecule with a single universally applicable molecular formula. Different precursor chemistry and assembly give chemically heterogeneous materials.

Dark eumelanin and sulfur-containing pheomelanin illustrate the family's diversity. Extended electronic interactions and structural disorder produce broad absorption rather than one isolated sharp molecular line. Consequently colour, composition and microscopic organization must be considered together when comparing melanin specimens; assigning a precise repeating structure to every biological sample is generally too strong.

An iron-containing tissue storage pigment, distinguished from iron-free bilirubin and haematoidin.

A light-absorbing molecule contributing to energy capture in photosynthesis. The absorption bands determine which wavelengths can be used by a particular pigment system.

A photosynthetic pigment that expands or modifies light harvesting alongside the principal reaction-centre pigment. Different groups can exploit different surviving wavelengths in a water column.

A phycobilin is a light-absorbing linear tetrapyrrole chromophore associated with particular photosynthetic antenna proteins. Its extended conjugated framework absorbs visible light.

Different phycobilin-containing complexes absorb different spectral regions, including wavelengths used less effectively by chlorophyll a. The chromophore's chemical structure and its protein environment jointly shape the observed spectrum.

A carotenoid is a member of a pigment family characterized by an extended conjugated carbon framework, commonly based on a forty-carbon skeleton. Conjugation gives these molecules strong absorption in parts of the visible spectrum.

Carotenoids can contribute to light harvesting and photoprotection. They can therefore broaden the usable spectrum of a photosynthetic system while helping manage excitation that would otherwise cause damage.

A pigment found in phytoplankton, including light-harvesting and photoprotective components. The assemblage spectrum depends on its pigment composition and intracellular packaging.